Get the Super POW
  Call up the map and press A, B, LEFT and START, all at the same time, then
  click on your inventory and you will see that you will have the Pass Key. Drop
  the Pass Key into a pool, and it will change into the Down Level, Drop the
  Down Level into a pool to get the Up Level, drop the Up Level into the pool
  and you will get the Super POW.

Get lots of weapons
  Call up the map, then press B, UP and SELECT at the same time to get lots of
  weapons and other stuff.

Drop down a level
  Call up the map, then press B, SELECT and DOWN simultaneously. This allows you
  to drop down a level from the level that you are currently on.

Warp to where you got defeated
  Lose all of your lives and continues, then take the Iron and drop it in the
  Pool of Fire to get the Glass Key. Go down the passage and use the key to open
  the door. Continue down the passage to find the Vitriolk. Pick it up and use
  it to be warped back to where you were before you were defeated.

Hints by Felipe Gerhard - felipe.gerhard@gmx.net