Unlock all boxers: Choose the cheat option at the setup menu then press: Start, X , Circle, Square, Square, R1, R1, Square, Circle, X ,  Start  

Invincibility: At the Cheat option in the setup menu press: Start, X, X, Circle, Circle, R1, R1, Square, Square, Start

Unlock conversation mode: Choose the cheat option at the setup menu and press: Start, R1, X, Circle, Square, R1, R1, R1, Start

Turbo mode: Choose the cheat option in the setup menu and press: Start, R1, R1, R1, R1, R1, R1, R1, R1, R1, R1, Start