Re: Electrum 4.0.2 imported wallet from Bitcoin Core, cannot send BTC cannot get key
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.
Electrum doesn't generate anything if you are importing private keys. When you say they look "completely not same" can you please provide specific examples? Does Bitcoin Core look like "bc1xxx..." etc... and the ones in Electrum look like "1xxx..." That is to say, the Bitcoin core ones start with "bc1" and Electrum starts with "1"? 
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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?
It honestly sounds like you have downloaded a fake version of Electrum or something... but the fact that the funds are still showing as "unspent" also indicates that they haven't been "stolen" 
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Can the Bitcoin Core public key be different for same wallet's different private keys?
yes... depending on how you import the private keys... If you just import the "WIF" key that was exported from Bitcoin Core, Electrum will default to "P2PKH"... which generates legacy addresses that start with a "1". as per the Electrum import info prompt:Quote from: Electrum Import Info
WIF keys are typed in Electrum, based on script type.
A few examples:
p2pkh:KxZcY47uGp9a... -> 1DckmggQM...
p2wpkh-p2sh:KxZcY47uGp9a... -> 3NhNeZQXF...
p2wpkh:KxZcY47uGp9a... -> bc1q3fjfk...
A few examples:
p2pkh:KxZcY47uGp9a... -> 1DckmggQM...
p2wpkh-p2sh:KxZcY47uGp9a... -> 3NhNeZQXF...
p2wpkh:KxZcY47uGp9a... -> bc1q3fjfk...
So... did your addresses in Bitcoin Core start with a "1", "3" or "bc1"?