Unlock All skills
     Finish the game with Leon. Save.
Choose "New Game" and type "@LLSKILL" as a name.

Unlock Play as Joachim Armster
     Finish the game with Leon. Save.
Choose "New Game" and type "@JOACHIM" as a name.

Unlock Crazy difficulty setting
     Finish the game with Leon. Save.
Choose "New Game" and type "@CRAZY" as a name.

Unlock Pumpkin mode
     Finish the game with Joachim Armster. Save.
Choose "New Game" and type "@PUMPKIN" as a name. 

Music test:
     Finish  the  game  as  any  character.  Purchase the Music Box at
Rinaldo's shop. You can hear any songs.

Unlock Jade Mask Item 
     Clearing the game will unlock the Jade Mask for sale at the shop.

Unlock Mobius Brooch Item 
     Clearing  the game on Crazy Mode will unlock the Mobius Brooch in
the shop.

Relics 
Wolf Foot - Found, Lab Locked Door 
White Bishop - Bought, Rinaldo's Shop 
Svarog Staue - Found, Castle Courtyard 
Saisei Incense - Found, Garden (need Wolf Foot to open door) 
Meditation Incense - Found, Waterfall (collect all gems in rail rides) 
Lucifer's Sowrd - Found, Ghostly Theatre 
Little Hammer - Found, Waterfall Ice Door 
Invincibility Jar - Dropped by Mirage Skeleton 
Crystal Skull - Dropped by Phantom 
Black Bishop - Found, House of Ruins Locked Door 

Keys
The hidden door keys are located in the following levels:

Red Phoenix Lock, Yellow Dragon Key: Anti-Soul Mysteries Lab
Blue Dragon Lock, Red Phoenix Key: Garden Forgotten By Time
White Tiger Lock, Black Turtle Key: Ghostly Theater
Black Turtle Lock, Blue Dragon Key: The Dark Palace Of Waterfalls
Yellow Dragon Lock, White Tiger Key: The House Of Scared Remains

Unlock Boss Rush Mode 
     Finish  the game with any character and save that game. Go to the
stage select room with that character.