Play as Cassandra
At the password screen, select the pictures of Mathayus, Menmon, Isis, and Mathayus.
Play last level
Enter password: Scorpion King , Cassandra, Menuth , Isis.
Cheat menu
Highlight the "Continue" option at the main menu, then press Down(2), Right, Up, Right, Up, Right, Down(2), Start. All stages and characters will be unlocked.
Level select
Enter the following character colors at the password screen: Menthu, Isis, Isis, Menthu.