You can't tell. Some refer to the hymen but it breaks easily and some are born without one. 80% do not bleed during first intercourse or feel pain. It looks the same before and after intercourse.
You can't. People say an intact hymen indicates a virginity but this is untrue (or at least highly unreliable) as there are many common activities besides sex that can break the hymen.You can't tell....
It really depends on the person.
But in my experience as a guy, when you haven't had sex before it seems glorified, like it's tenfold whatever masterbating is like. It's hard to imagine what it's...