Yep the issue is, why i couldn't see them on same wallet.dat that was older and synced, but could see them in later one which is basically same wallet. Remains mystery to me. Keys should be same, but this is not related to electrum.
No i don't use private node or local one. My wife is able to use sign and broadcast fuctions on Electrum, i cannot. Something was definitely screwed up in my electrum wallet. Probably it was bugged from long time ago when i created it. But in end of 2019 i think it was already 3.3.8 so shouldn't have happened. Well hope it's a single case like this. As i was not able to find anyone with same issue yet. However for now i will stick with Core. Better wait 2 hour to sync than lose everything because of bug.

Electrum was fine, except that it couldn't send anything out and bugged export keys commands in console and gui. Electrum seems like was unable to find/link this keys to private keys until i synced the actual latest core wallet to blockchain. Wish i knew what the issue was exactly. Just magic no logic.

At a time i made it, i imported all keys found in Core which was 3. Later i dug out more but this is not releavant to the problem. Multiple addresses in amount of more than 100, was derived from this keys and some unknown keys to me looks like. As Newly created Electrum with same addresses do not show any new transactions. So, it looks like, there is keys that Bitcoin Core did not show, even tho they are there. Since Core has no command to Display all priv keys.

Wallet.dat is for the core, i was unable to see transactions made in Electrum on old wallet.dat in Bitcoin core. So when i made backup i thought all Wallet.dat files supposed to be same, with 1 master key. Obviously i was wrong. It missed something, that did not allow me to see transfers. When i put latest version of it i was able to see them.

If you don't understand you just cannot, took me 3 days of trying everything anyway to fix this.
If you didn't read about it before, if you import keys to Electrum both Core and electrum becomes 1 wallet basically. Anyway i will delete all this old stuff and make fresh ones. To avoid such a clutter of old stuff.

As i suspected after 3 days of trying. Issue was in old wallet.dat file. It didn't have some hidden new master keys or private keys. The amount of displayed addresses didn't change. But after i used latest wallet.dat all transactions showed and funds was taken out swiftly because now i need new wallet due to, to many manipulations trying to fix it.
Problem is Electrum picked up that new hiden addresses and send funds to them. And i still cannot see any new addresses or keys in my Core. They came in as brand new addresses i never seen before. But non the less it was received.
Also another issue that stands, is electrum Crashing when trying to display private keys from imported wallets as well as from GUI or Console after updating to 4.0.2, alltogether or single. Also forever disabled buttons to sign or broadcast. Unable to send funds through console. Seems it cannot connect to servers well enough to process transaction. I would recommend for people using Electrum to switch to core. To many bugs in Electrum. So much again for Newbie friendly easy wallet Well i am happy now finally i can sleep well.

I have no idea how 2 addresses worked and rest didn't actually the strangest thing this was not the first transactions that worked, it's more like in the middle of them. Earliest ones are lost and the latest ones too. Guess i was just if you can say "lucky" to hit the addresses assigned to correct keys with 2 transactions. And one which is real strange, has been imported as watch only from Private key, i don't know how it's possible even.

Still same result, that addresses that was caught up from Electrum is there, but rest is still missing.
Electrum just bloated out bunch of keys that has no connection with Private keys given and didn't attach any keys to this addresses... Basically lost shitton of money to the air. I guess best idea would to be patient and never stop using Bitcoin Core. As this is not hack or anything, this is loss because of the Electrum numerious bugs and this is not the 1st one that made people lose access to funds. Old wallets unaccessible now because of password corruption, no way to recover data for imported wallet, new 4.0.2 Elecrtum cannot broadcast or send funds actually, even through console. When password enters sometiems the error comes out that it has 4 symbols instead of something until its restarted. To many bugs... Their own wallet is cool and all if you make new one, but it should not make people lose money because there is such function to import, that does not work as intended should disable it and not let people lose their stuff. Not the first corrupted wallet issue.

Basically i tried everything i could try nothing worked. Now i am just trying all backups from Wallet.dat, but i am pretty sure its waste of time. As i never had such keys as Electrum assigned addresses to.

Could this happen if i used older version of Wallet.dat and there is later one available with possible more addresses ? Damn core is scanning blockchain again, which takes ages so i cannot check that option.

Even tho i am already tired as hell of trying all options possible (so much for newbie friendly software with no recover options in case of imported corrupted wallets)...
I will try to explain how i got part of transactions.

Wallet was created by importing keys from core pretty straightforward.
Then after i couldnt transfer funds and couldn't see them on other Electrum wallet, which is strange since i used same private keys. All this transactions even the ones i see on core now, didn't show in new imported wallet.
I took the priv keys from electrum back to Bitcoin core and was able to see 2 addresses transactions out of 13.... now go figure what the hell happened. That means that part of addresses generated from electrum belonged to old private keys but most belonged to new ones that Electrum didn't register in Wallet file...

Yes basic structure of file looks fine, i can see it and open it without encryption.

I received transactions on core from 2 addresses. 1 showing as Watch only and rest didn't show on core.

Basically downloaded Blockchain for Core past the date of transaction, i cannot see it. It is really that problem with corrupt wallets. Except i don't remember creating any standard wallet prior to making imported one. So who the hell knows how to get funds out of this damn electrum now.

I found deleted Default wallet on one of the shadow discs and recovered it, however none of my passwords match. Could that be the answer. It was created in March, i don't remember deleting any wallets in march. So i have the wallet now. Now i need to figure how to brute force it... Obviously i would remember my passwords.

It's 100% not watch only.

Drive is normal hard drive which is slow but very stable model. I might of generated Standard wallet previously. But not one after another very fast. It says imported wallet, not watch only or standard.

Small update.

It seems like i seen payment requests arriving to my Bitcoin Core wallet, so it seems like that is why i am unable to sign transactions through Electrum. They ask me to sign it in Bitcoin core? That payment request was added on Electrum but looks like they show in Bitcoin core. So it might be a good sign.

The problem is as mentioned above. I have only select private keys, the Addresses that Electrum made from who knows where, i cannot get private keys for them due to KeyError in right clicl drop out and in console. So i am either arleady screwed by Electrum, that it bugged and failed to save Private keys for my received transaction, or this new addresses belong to same Private keys, but i cannot see them in new Electrum wallet. So basically its a limbo. Now i am waiting to see if Bitcoin Core will show this. But i kind of really doubt that. It seems like either when i update Electrum or even long before that it was already bugged. Doesn't answer the main problem however, how to get my funds out of Electrum now... As i do not have private keys for receive transaction made in Electrum. I also checked wallet itself, it has only addresses i imported. So if i reach the Blockchain sync date that i received 1st payment to my side and i cannot see it. I have no idea what to do.

Is Addresses and Private keys created by electrum stored in Wallet? Or they are stored in some library or decrypted inside some file? Because if it's the wallet, only one that hold information i probably won't ever get them out, as keys is not there. Seems like older version, started generating new addresses for me, on imported wallet before. And of course since there is no new keys for imported wallet, probably new version just deleted them when converting, or they was never actually stored because of the same bug.

I found old wallet installation file, it's downloaded 01.08.2019 and it definitely legit signed installation of Electrum. So it's not possible i got bad version that was fake or hacked.
Now the question is what happened and how. With mostly offline disconnected from internet PC.

Well i geuss seing funds doesnt mean they belong to me, only way i see this happen if there was planted in some way addresses or copy of Electrum that looked like electrum that generated someone elses addresses.
I did import same keys before to new electrum wallet and of course i cannot see any of that transactions. However as i mentioned before even new wallet unable to send transactions sign and boradcast are still disabled. Could that be because of the Bitcoin Block chain not fininshed downloading and i need to sign them from Bitcoin core? Or provide some confirmation on core itself. Don't know how this electrum works, if i cannot even send 100% funds that i own and can send from Core.

I already did extract Private keys from that wallet, they are not different from ones that i put in there before wit hexception, which is strange about 2 or 3 additional private keys i got when i returned keys to Bitcoin Core, one of them i cannot even get priv key from in my own wallet after import. I compared new wallet and old one, they are identical structure and code wise. I tried to manually reverse to 3.3.8 but it just aint working, guess the structure was not same, even tho it looks so similar after all it's just strings with info. Still waiting on Core to download blockchain. It's really not possible that my ancient 2 cents (over limit of minimal transaction) from new wallet also cannot sign and transfer. Even if problem was with connection i tried VPN result is same, sign and submit buttons are disabled.

I don't think imported wallet has master key, well even if it does i cannot extract it from Electrum i get error, i would try to punch it to Core. I guess it doesnt even have one as it's imported.

The Funds still show available in full in my wallet, Electrum 4.0.2 which i got 100% from official download source. Nothing was ever spent from this wallet. All the receive addresses are still there in the wallet, the addresses that funds was received. None of it is spent. Neither can i sign any transaction to send them out. Either someone who was stealing them this way screwed up an i ended up with locked coins forever, or old Electrum version had serious bug where it created new addresses without seed for imported wallets. 

Some start with 1, some with 3 and some with bc1. The electrum ones all start with 1

The new wallet i made only uses imported private keys addresses. But old version of Electrum seems like generated fake ones to receive that dont belong to me. Or at least somehow they look completely not same as on Bitcoin core.


Could it be that someone has planted a lot of fake addresses to my Electrum, so the generated addresses do not belong to private keys? Can the Bitcoin Core public key be different for same wallet's different private keys?
The strange thing is there is like a 100 of receiving addresses a lot of them with 0 transactions. Obviously i do not have so many private keys for so many addresses. All the transactions received is unspent, so i doubt it was stolen. But the problem is i cannot get private keys from any than 5 i originally imported. I tried to find anything about this kind of attack or hack in the past on electrum, but it just doesn't match.

Basically Electrum generated bitcoin receive addresses previously that obviously do not look like Bitcoin Core addresses keys i imported. And no one had access to PC except me, it was offline most of the time. Hard disconnected internet and no wifi cards on it. It just looks like it made up random addresses for receiving with different public keys.

Just as update, importing private keys to fresh Electrum wallet does not show funds received by electrum.

But in old electrum wallet they show and show as confirmed and available...

Really not sure what is going on, only can tell after another 150gb download of blockchain.