Acquire All Skills Mode 

Once you beat the game, save your progress. Start a new game on a separate memory card block (do not overwrite your first Castlevania block) and enter your name as @LLSKILL. 

Unlock Boss Rush Mode 

Once you beat the game, save your progress. You can go to the stage select section and have a hand at the Boss Rush Mode.

Unlock Crazy Mode (Super Difficulty) 

Once you beat the game, save your progress. Start a new game on a separate memory card block (do not overwrite your first Castlevania block) and enter your name as @CRAZY. 

Unlock Jade Mask Item 

Beat the game and you'll unlock the mask at the shop.

Unlock Joachim's Game 

Once you beat the game, save your progress. Start a new game on a separate memory card block (do not overwrite your first Castlevania block) and enter your name as @JOACHIM. 

Warning: Joachim doesn't have weapons, armor and cannot pick up health kits. His game is extremely hard.

Unlock Mobius Brooch Item 

Complete Crazy Mode and you will get the item in the shop.

Unlock Pumpkin Game 

Complete Joachim's game, save your progress. Start a new game (do not overwrite previous CV block) and enter @PUMPKIN.

Note: You'll get all skills and the Vampire Killer. Your stats will be improved, but you will not be given any subweapons other than the one you first get.

Unlock Sound Test 

Complete the game, and save your progress. You'll be able to buy the Music Box in the shop. Once you buy it, save your game.