Master code
Go to name entry screen at career mode. Enter GIVEALL as a name.

Hidden board park
Go to the name entry screen at career mode. Then input EVRSPRK as a name to access a hidden course.

Bonus characters
Finish the diverse challenges to access Tara, Nate, Replay, Max and more bonus characters. Finish all hard downhill gates to access Le'Monjello, Burg, Tex, and Gray.  

Bonus event
Finish all events to access the Triple Crown Event.