Unlock Original Prince of Persia:
When you get the second sword (that can break walls) keep on going until you break a wall and the prince says "It's said they built this palace on the ruins of another..." Across the next room you will come to a switch. Break the wall behind that switch, it may take a few ties. Rotate the switch to point to the new room and open a gate to the original Prince of Persia.
Unlock 3-D version of original Prince of Persia:
Start a new game and stay on the balcony. Hold L3 and quickly press X, Square, Triangle, Circle, Triangle, X, Square, Circle.