To be able to get Richter's whip to lengthen slightly when he attacks so it becomes a more effective weapon you can either press the attack button followed by forward twice or if you are jumping or crouching hold the crouch button and press the forward button twice. If you've entered either code correctly the whip will turn white during the animation.
Unlock Maria as a Playable Character in Castlevania: Rondo of Bl
Collect the candlestick that has the 'key' subweapon when the Minotaur is chasing Richter and then enter the sewers to escape him. Follow the sewer path to the end to where there is a locked door and use the subweapon to unlock it. This will trigger a cinematic scene of Maria joining Richter and she can then be unlocked as a playable character at the 'Main' menu.
Unlock original Dracula X: Rondo Of Blood in Dracula X: Rondo Of Blood: When you get to the end of stage 4 there is an area where the bottom part of a wall can be broken to reveal a bomb. Explode the bomb to blow up the wall and then enter the area that was behind it. Move towards the platforms and defeat the Axe Knights and look in that area for the item that unlocks the original Dracula X: Rondo of Blood.
Unlock Level select in original Dracula X: Rondo Of Blood: When you begin a game enter X-X!V''Q (including the two apostrophes) as your name.
Unlock Castlevania: Symphony Of The Night in Dracula X: Rondo Of Blood: In stage 2 when Richter is being chased by the Minotaur jump into the first hole to enter the sewers and then defeat the boss there. This will unlock the alternate version of stage 3 where you must always select the upper route everytime your path splits. Make sure you collect the axe when it appears as you will need it to chop the vines which are covering the cage when you get to it (the cage is found near the skeletal snake that is hanging on the wall). Use the cage to jump on to the upper ledges and continue along them until you reach a tombstone which when you break will unlock Castlevania: Symphony of the Night as an option at the 'Main' menu.
Unlock Symphony of the Night Modes Before you can enter these passwords you must first complete the game including the Inverted Castle as Alucard. Then you can enter these case sensitive passwords as your name when you begin a new game to enable the corresponding effect in it.
Unlock Maria Renard as a Playable Character: Enter the password MARIA
Unlock Richter Belmont as a Playable Character: Enter the password RICHTER
Unlock Alucard with the Blue Axe Lord Armour as a Playable Character: Enter the password AXEARMOR
Unlock Alucard as a Playable Character with 99 Luck and the Lapis lazuli (+20 luck) Accessory: Enter the password X-X!V''Q (including the two apostrophes).