Not true. The reality is you can either have something fast, and irreversible, or go with the more trusted but slow approach: Escrows. There are ways to lock a transaction (wallet if you will) with M of the N keys approach. meaning you need only M keys out of N keys to unlock the transaction. You can use similar mechanism to implement nuclear codes (as an analogy), where you need 3 different people to approve launch, out of 5 possible people (two of which might have died).
For public blockchain ones, yes. All of the transactions are visible.
For things like monero, it’s on demand. You can ask me (for example subpoena or for IRS tax forms) my view key to view where the money is coming from and how much. You can, however, decide to hide everything.
Not sure what you mean.
If you can find them. For public blockchain, there’s a possibility as they will need to cashout and exchanges are government regulated (to an extend), but still possible.
For lost keys scenario 2 out of 3 key system would probably work.
For things like monero, no.Once it’s in the system, you cannot do anything. Which is also the good part. Government probably shouldn’t be able to seize your money if you obtained it with legal means (selling good), but the buyer used stolen/fraud money, for example.