The following arenas become available options in Versus mode when the indicated amount of Team or Arena Battles have been won.

Unlock Elephant Pool Arena:
Win 20 Team Battles.

Unlock Metal Age Arena:
Win 100 Arena Battles.

Unlock Extra Health and Speed:
If going to play Versus or Team Fighter mode and need some extra health and speed then at the 'Title' screen press Down(2), Up, Down, Left, Right, Down, Up(4), Right, Left, Square.

Unlock Alternate Team Fighter Characters:
At the 'Character Selection' screen in Team Fighter mode press L1(2), Down(2), R2, Select, R2, Select, R1, L1, R1, R2(3), Select.

Unlock Alternate Versus Mode Characters:
At the 'Character Selection' screen in Versus mode press L1(2), Down(2), R2, Select, R2, Select, R1, L1, R2, R1(2), Select.

Unlock Large Characters at World Map:
At the 'Title' screen press Left, Square, Up, Circle, Right, Triangle, Down, Triangle.

You can't immediately damage an enemy that has been frozen, another attack will only break the freeze without harming the enemy. They will though be stunned and vulnerable to another combo attack.