All Bonus Items:
Collect all 100 Crystals in the game. 96 can be located in the games levels. 
However there are 4 hidden very well.

Infinite Mana:
Enter Sound Options. Select soundtrack. Listen to tracks 7, 3, 1, 5, 8 in that order. 
You will now have Infinite Mana once you start a new game. This code cannot be 
used with a save file.

Extra life:
Collect ten crystal heart pots during game play to earn one extra life. Note: Each 
level has five crystals. 

Final four crystal heart pots:
There are four crystal heart pots that are not found in the normal game. To collect 
them, intentionally die and go through the Beach Of Souls to the next Beach Of 
Souls with the lighthouse. Then, get through the sequence of jumps sequence that 
are timed by the firefly to get the last four crystal heart pots. Note: Collecting 
these and all the other four crystal heart pots in the normal game will give you a 
total of 100 of them.