Zoomaroom Cheat mode
After you hear “Zoooomaroooom” at the title screen, press LT, RT, LT, RT, X(2), LB, RB to unlock all costumes, all tiers (including the bonus tier), and the double-jump. If you entered the code correctly, a coin will appear at the bottom right corner.
The image featured at the top of this post is ©The Legend of Heroes: Trails of Cold Steel III key art / Original