Go to the options screen. You can reach it from the main menu. Hold L2 and press Circle to unlock debug mode.
Expert mode
To unlock a hard difficulty setting, complete arcade mode without continuing.
Get Uranus & Kohryu
You can get Uranus and Kohryu very easily, you only need to win the game with anyone and with the difficulty you want.
But, you can't use the continues, you can't lose the 2 rounds in a fight.
Hidden modes
Defeat more than 10 opponents to unlock a bonus mode. Keep winning to unlock more modes.
High speed mode
To unlock high speed mode, win 100 fights in survival mode with one character.
Highest Difficulty
Successfully complete arcade mode without continuing one to unlock the highest difficulty level this only work in survival mode.
Hyper Beast Battle Mode
In arcade mode, fight 10 battles with the same character, then rank in with the same character in arcade mode to unlock Hyper Beast Battle mode.
Low speed mode
To unlock low speed mode, obtain a ranking in arcade mode with all characters.
No blocking mode
Obtain first place in arcade mode to unlock no blocking mode.
No Guard Battle Mode
Finish arcade mode in first place to unlock No Guard Battle mode this only works in survival and vs.modes.
One fall mode
To unlock one fall mode, win twenty rounds in survival mode with one character. In this mode, the first character to fall will loose, but they will be invincible to all other attacks.
One-hit knockdown mode
Obtain first place in sudden death mode to unlock one-hit knockdown mode.
Sudden Death Survival Mode
Complete survival mode by winning nene figts to unlock the Sudden Death Survival mode.
Sumo Wrestling Battle Mode
In arcade mode, fight 20 battles with the same character, then rank in at surivival mode with the same character to unlock Sumo Wrestling Battle Mode.