First go to the constructor (not the challenges) then build the biggest ramp closer to the wall. Then get the cheats for unlimited nitro. Next get that fast car that looks like a Ferrari and take it off the jump while rapidly pushing L1 and watch your car FLY!!!
All u have to do is get 3 or more stars on the third chapter.
enter "KUNGFOOPETE" as a code in the cheat menu
at main menu select extras then cheats then enter "RANDARLUV"
all u need to do is get three stars on each scene