I think you do not get my point of view, I just want to know that in an IDEAL WORLD, the Electrum wallet on the computer with an internet connection is safe if there is no Malwares, no hacker's attempt etc
We use Cold Storage only to avoid any possible risk that comes through the Internet, Right? There is no other reason.
1- If we connect the Internet to that machine once or sometimes (to update the Electrum wallet) , will it not remain a cold storage?
Technically No.
But still possible, Yes?
2- If we are sure that there is no malware or something in the computer, what difference does it make to connect that cold storage computer sometimes to the internet to make transactions?
As per my understanding, we do not connect cold storage to the internet because we fear that any malware may get our electrum seeds etc. Is is right ? There is no other reason. Connecting to Internet, does not mean that the Internet will know the private key or leaks your private key.
The actual purpose of creating the cold storage for crypto wallet is to mitigate any potential vulnerabilities so in case if you want to take the risk that you can be sure the device is entirely malware free then it's your choice.
Look here, you said "potential vulnerabilities". if we are sure that there are no vulnerabilities in the system, then we can connect to the internet.
3- If we install electrum on computer (which is malware free and connected to the internet), make a new wallet, keep a note of the seeds and then uninstall electrum from that computer and also remove the wallet files, isn't it secure too?
Uninstalling and deleting doesn't necessarily mean files are gone permanently because we know it is possible to retrieve data back even from the formatted hard drives.
Again, assuming the computer never gets stolen, uninstalling the electrum keeps the coin safe even if some malware later comes in that computer and we never re-install the electrum in that computer without formatting it first.