Automatic Health Regeneration
Connect your GBA to your GameCube. You must have the GBA PoP game in your GBA for this to work.

Unlock Original Game Without Using the GBA
To unlock the original Prince of Persia game without using the Gameboy Advance, you'll need to start from the Above the Baths save (once you have your new sword). Go down the stairwell that leads to a large cavernous area. After you make it through this area, you'll end up in a small room with Farah. There are a lever and a gear in the center of the room. Turn it clockwise until it clicks twice. Both doors in the room are now closed, but you'll also open a secret door that you cannot see. Go to the wall directly opposite the entrance. Swing until you find a spot on the wall where your sword doesn't spark. Strike this area a few times to reveal a hidden room. Enter to unlock the game, which is now available on the main menu

Unlock Original Prince of Persia
Find and activate the three special GameCube switches in the GBA version of PoP, then connect your GBA to your GameCube