To unlock all the soundtest, which include over 35 classic Neo Geo tunes, simply unlock the Neo Geo Land stage, which is the 4th stage you unlock, by fullfilling any of the 4 requirements to unlock a stage.
Extra Outfit Colors
There are several methods of unlocking additional colors for each character's outfits. You can get up to 4 extra colors (E, F, G and H) for each charcter's Normal and Another outfit. Select the character and outfit of your choice, then do one of the following:
Effect - Code
Extra Colors - Clear Story Mode
Extra Colors - Clear any Mission in Challenge Mode
Extra Colors - Clear Time Attack Mode
Extra Colors - Awarded every few stages in Quest Survival
Fio
Beat the game 3 times with different characters.
Hanzo Hattori
Beat the game 4 times with different characters.
Hard Missions
Succeed in all 10 levels of Easy Missions to unlock Hard Missions.