Although it is not easy to guess someone's private key, if you guess someone's key, then you have become its illegal owner. Whether the asset is stolen or found on the street, you are not its real owner. Now you have mentioned one point, now if the real owner of a wallet dies, then his children or his heirs have the right to claim it, but you cannot become its owner by guessing it. If you do this, then it will become illegal.
I don't remember my own key, sometimes I make a mistake while accessing the wallet. How can I guess someone's private key there, ha ha.  

Any wallet containing coins retains its rightful owner, even if someone manages to guess the seed phrase. Bitcoin wallets differ from bank accounts, where the bank provides legal safeguards for account security; Bitcoin wallets operate without a third party, meaning individuals are solely responsible for their own private keys. If someone accidentally guesses the seed phrase, they could transfer the Bitcoin and claim the funds. They might well avoid legal repercussions, as tracing the person who guessed the phrase and took the assets would be extremely difficult. In fact, many wallets remain inactive for long periods because the owners have disappeared or completely forgotten about them—implying that someone who successfully guesses the seed phrase could possess the coins without fear of legal action. Nevertheless, both morally and legally, I consider this an act of theft.

Yes it is impossible, only an idiot would hold funds in a single wallet, although that wallet can have more addresses that's a different thing but keeping that much funds under a single seed phrase is the most idiotic thing to do so that's why we can never find $1 billion.

Also rich people like this one here, always use multi signature wallets, so one wallet won't do any good that's why it is best to not wish for something this delusional.

Instead be moderate like expect to get $1 million to $10k that would be enough but I will not use them, and secure them until the real owner claims it back using the right key. But the key alone is not the only factor for verification, I will definitely demand more.

I don't think guessing a private key is possible. A dormant wallet that wakes up might have different reasons maybe the owner is ready to use it or maybe the person is lucky to get the keys as you have said. If a key is generated randomly that has bitcoin then it isn't illegal. In bitcoin who can sign owns it.

Talking about if the owner is alive the owner can sue as legally its seen as theft. But if the owner is dead and no other person to claim it then you're lucky. But the problem will be when the coin is moved to a kyc wallet it can be traced. That's why we need to know law doesn't support theft even if it's gotten by luck