not all of the prototypes are unlockable, but you can unlock most of them by doing sponsor challenges and beating the story mode which gives you a few. you really can't get every part which means...
Yes it does however, it's nowhere near as good as ATV Off Road Fury Blazin Trails. You can't venture off the track without getting the 3 second warning. So yes there's free roam but you can't go off...
