The people who are still holding, or the people who sold at its height, to people who were hoping for more? If the former then they haven't gained anything yet, if the latter, that's the greater fools.
The top so far. I have no idea about the future. Regardless, when do people sell? When it's at the top? When is that? If it's going up shouldn't you continue to hold? And should you sell when it drops? You haven't. So what's your line in the sand? Should new people be buying in? When should they stop? And then who are you going to sell your coin to? The greater fool.
Comparing bitcoins volatility to fiat is ridiculous but regardless, you haven't made any actual guaranteed monetary gains until you sell.
Ok, sure, avoid the other questions, but to be clear, paying for something with bitcoin is the same as selling it, you're just pretending that there isn't a conversion to fiat somewhere in the chain.