Complete the game and Prince of Persia 1 will be playable in the extra options menu.
Unlock Prince of Persia 2
When you receive a new sword around 33% through the game, continue on until you break a wall and the Prince says, ''It's said they built this palace on the ruins of another...'' Once you cross the next room, you will find a rotatable switch. Directly behind this switch is a breakable wall, although it doesn't appear to be. If you hit it three times, you will find another room and you will receive a message informing you that Prince of Persia is now unlocked.
Note: You can also rotate that switch until it points to the new room and it will open a gate that allows you to play Prince of Persia 2 right there without having to exit back to the Extra Features screen.
