Zelda games are great, The Master Quest is hard but this one is harder...

After you save Medli she gives you the "Grappling Hook" Go up the stairs and use your G.H to get to the ledge oppisite you now keep going and you'll come to a ledge.

Jump down and you'll be at the bottom of the staircase that collapsed. Directly left of where you land is another Grapple stick. keep "Grappling" down till you find a door.

Inside is a bridge, defeat the Bokoblin,(The thing biting the bridge) and keep going across in a jar there is another Bokoblin defeat him, now either burn or cut all the suspension wires to the bridge and you will fall. Open the chest, then go into the door opposite.

On your right is a platform held up by three cords inside a cage. Use your spin attack to break them all at the same time. The platform will fall down into the lava surrounded by teeth like rocks.

Jump into the entrance nearby and jump platform to platform when you come to the locked door,
use your grappling hook on a ledge above you.

It will open the door. Inside keep going until you reach the chest with fire around it next to a switch. Stun a magtail (the scorpions) and put it on top of the switch.

Inside the chest is the Boss Key. In the room before with the big boulder and all the skulls, just before you free Medli, on the other side of the lava is the Boss Door.

Au revoir and Good Luck.

After you save Medli she gives you the "Grappling Hook" Go up the stairs and use your G.H to get to the ledge oppisite you now keep going and you'll come to a ledge.

Then throw the fishing hook to tjhe other ledge of the cliff.

Medli will give you a grappling hook.

Anyway you got the wrong game lol.