Apparently, Bitcoin preserves anonymity of users such that nobody is able to know who is behind of an account address. But If this user intends to exchange a bitcoin with a formal currency, eventually they need to reveal their personal information, isn't it? Or is there a way to keep anonymity even at time of exchanging with formal currency?
You are possibly looking for a Bitcoin ATM or a private transaction with a cold wallet. There is no real anonymous way to exchange for fiat over the internet. Most exchanges have regulations from the government in place that require you to verify to fight money laundering. Also it would force you to verify a bank account that needs a name.