Everything is legal until the appropriate laws that make it illegal are established. Since the law decides what is and isn't legal, if there are no laws that say BTC can not function without proper regulations it remains legal. You are right thinking that BTC isn't a bank account nor stocks and since your wallet isn't assigned to your name you don't have to inform the government.
I hope that answers your question in full
Yes, I agree with your answer, I think the use of bitcoin is all legal, no one forbids it, but it depends on the government in their respective countries.I hope that answers your question in full
For what the government knows if the government does not legalize the use of bitcoin, I think that is not an alternative, but that is a problem in the future. Because in some countries, their government does not legalize the use of bitcoin.