“unknown rules (versionbit 2) have been activated”
This means that you are probably using an old version of Bitcoin Core that doesn’t understand new types of Bitcoin transaction. The current version is 0.21.1.
It almost certainly has nothing to do with the second part of your question.
Installing a new version of Bitcoin Core from the genuine website should make the message go away. It won’t get your money back though.
Bitcoin Core made a transaction by itself
If you didn’t make the transaction, either someone else has access to your wallet or to a copy of your wallet (that is, they have had some kind of access to the private keys in the wallet). It is possible your computer has malicious software on it that you were tricked into installing.
Don’t download software from trickster websites that use variations of the name such as “BTC Core”. Mistakenly installing malicious software is one way of having money stolen. I note that there is a site whose URL spells bitcoincore with an accented ń – I can only assume it is a fake website providing maliciously altered software that steals money. That malicious imposter website seems to have currently bought its way to the top of the Google results (it’s an “Ad” result). bitcoincore.org is OK, bitcoińcore.org is fake.
and sent all my bitcoins from wallet to address I don’t recognise.
That sounds like theft.
Can I do something with this issue and get my bitcoins back?
You can’t cancel, undo or reverse a confirmed transaction. Only the person or business who controls the receiving address can create a new transaction sending the same amount to you. It is possible the money has been moved further.
Beware of fake recovery agents. You are much more likely to be tricked out of further money than to any see any significant amount of stolen money returned to you.
See
