Here are the 5 special/hidden tricks.
They were done from a Xbox controller.
To make them count, you'll need to land them and not fall.
Danny >> Rocket Backflip >> Left to Bottom then "B".
Sean >> Kickflip Late Shover >> Right to Top then "X".
Lyn-Z >> McTwist >> Full circle clockwise from Top then "B".
Christian >> Christ Air >> Left to Right then "B".
Ryan >> Impossible Late Flip >> Left to Top then "X".
(Credits to FEAR EPIDEMIC & JJBDude48)