Play The Demo
Set the difficulty to Hard, then enter the password: B J Q X Y R K C D L S Z. This allows you to control the character and fight through the demonstration scene. You will have two chances to fight two creatures: a warrior on a horse, followed by a large skeleton dragon.

See The End Credits
Set the difficulty level to Hard, then enter the password: M T k M S k T k H N S H. (To get to the lowercase letters, select Page on the Password screen)

Fight New Bosses
Go to the Password screen and enter the following password: X x x x Y y y y Z z z z. (choose Page to select the lowercase letters) This allows you to fight Tanzra's final form, a giant Centaur. Then continue right and you will fight against the end boss from the original ActRaiser game.

Go to the last stage of the game
Enter the following password MFMJ TVSY FVPX.

Activate Death Helm
Enter the password MFCL SYMC MSXF.