Legend Of Zelda 2: Adventure Of Link Hints

In some castles and action screens it is possible to jump higher than the stats at the top of the screen. If the spell Fairy is used when Link is above the stats and you try to move to a side, he will fall through a warp hole. In the action screens Link will simply reappear on the same action screen. While, in the castles, he will end up on top of or in another room, on top of the castle entrance, or in an elevator below the castles entrance and stuck. If he gets stuck below the castle, you will need to reset the game. Also, the spell Jump can help with this glitch.

Lose all three lives and select "Save." Or you can pause the game and press Up+A on the second controller and select "Save."

If you come to a locked door and hove no key you can simply use the Fairy spell and fly right through the keyhole. And sometimes if you have enough magic you can make it through the whole palace just using this trick.