Rondo of Blood Passwords
At the name screen enter:
X-X!V''Q (that's 2 single quotes, not a double quote)
for access to all the levels.
Maria's Special Attack
As Maria do this move:
Quickly press Down, Up then Down/Forward + Attack
This projects Maria's alter-ego, it causes MAJOR Damage.
Castlevania Games - Rondo of Blood - Rondo Passwords