Really difficult...
I didn't know the answers to most of those and I'm a diehard Sonic fan XD. Liked the music.
BTW on the second question, it's Nack the Weasel (or Fang the Sniper, whatever you want to call him), not Nack the Beaver.
For the fourth one, if there is one, you should add questions about the TV shows, multiple difficulties, and perhaps a choice of different music. That would be cool.