For your first few questions, read any of these threads
or this one here
. We have a whole board dedicated to fursuits.
For the others:
Why do you have to tell your parents you are a furry? If you are getting a suit, I can understand it, but otherwise I do not see that there is a reason for them to know. If you are worried about how they would react, I would urge not getting a suit until you have moved out. I've never told my parents. It's a hobby for me, and they don't need to know all my hobbies. If you do feel you have to tell them, don't treat it as a big, horrible secret, or they will act like it is one. We have threads on this as well, if you have a bit of a look around.
A person can have as many or as few fursonas as they please. There is no rule. If you want one, have one. If you want a dozen, have a dozen (but don't expect people to be ab;e to remember them all). It's entirely up to you.
I've never been to a con, and have no real interest in going, so I can't tell you what goes on at them. But again, we have a whole board dedicated to cons. If you read some of the threads in there, that might answer your question.