As other people have been pretty generous with details on your first 2 questions, I'll simply add a little more to what has been said regarding places to meet people before the convention starts.
1) As of past years, some activities were organised on Thursday for those arriving early in town. Of course we don't know yet for sure if there will be anything of the like this year on Wednesday, but it still makes room for good occasions to meet new people if you can roam around the area that evening!
2) Even before it starts, you will often find yourself in situations where the other people around you are also attending the con; restaurants, hotel elevators, convention centre lobby, badge pickeup, even the opening ceremonies waiting line, etc. From what I've understood, you own a Diamond Sponsor, so you will have the opportunity to skip ahead the huuuuuuuuge normal line, but you will not be alone for sure!
3) The ambiance at BronyCon is all about meeting other people and having fun together. You will most likely end up interacting with plenty of other folks (of course, that is only if you want to). Don't be afraid to speak with everyone at your favourite panels and activities!