Moto GP 4 Cheat mode
At the main menu, press Up + R2, Right + R1, Down + L1, Left + L2, L3 + R3 to unlock all bonuses. If you entered the code correctly, you will hear a sound.
Legends mode
Win the 125cc, 250cc, and MotoGP championships to unlock Legends mode.
BMW 645C1 pace car
Win the 125cc championship to unlock the BMW 645C1 pace car.
The image featured at the top of this post is ©The Legend of Heroes: Trails of Cold Steel III key art / Original