It must be your baby molars which will be replaced with adult premolars. Don't worry. It wont be a permanent tooth. Roots of baby tooth must be resorbed, that's why it must have come so easily.
Yep. All of my molars fell out, don't worry about it. :)
Well, it isn't really good at your age because one won't grow back in it's place, but it's fine. If you are getting braces later on it should all be good.
I dont think that they are supposed to, but if it needs to be pulled out then have it done, but if it starts to become loose your mouth wants it out