Racing games don't limit your track selection if you want to play with friends. And definitely not if they only have 5 tracks.
Anyway but eventually I did bother to do the sonic speed championship but super sonic is way beyond what I can do. Well since I'm better at disassembling games than racing, I'm probably gonna find another way to unlock it. Looks like fun stuff for tweaking actually.
Edit: okay that's one fine track, now again why would you lock the best track int he game? Crazy