Go back down and pull it. You need the gate open to reach the cell. (see the related question)
Still in the dungeon. Either the hole is too small, or he doesn't like dirt caves.
Go back in and pull it. The dungeon will not be guarded until you pull the switch and take the cheese.
The only things you do in the castle dungeon (under the library) are pick up the cheese and throw the switch. (see related question)
Throw the switch when you get the cheese. You can enter the dungeon from Mordred's underground laboratory once you have the robot owl. (see the related question)
Push through the dirt wall. You should already have opened the back gate with the switch in the dungeon. Feed the mouse to Merlin. He can retrieve things for you.
The switch in the dungeon opens the back gate to the cell. Later, you can enter that way through Mordred's underground laboratory. (see related question)
You have to come in the tunnel that Mordred first dug to escape. When you flipped the switch in the dungeon, you opened the gate at the back of the cell. You can get in that way if you reach Mordred's hidden laboratory.
The small gate is in the BACK of the dungeon cell, and connects to the tunnel Mordred dug. By throwing the dungeon switch, you open the gate so you can come in that way. (see related question : getting back in the dungeon)
The key in the dungeon doesn't work. You throw the switch and come into the cell from the back way. (see the related question)
You don't. Once you have gotten the cheese, and pulled the wall switch, that is all you can do there. You will have to enter the dungeon from Mordred's underground lab, through the tunnel he dug to escape. (see the related question)
You really can't do anything else once you get the cheese and throw the switch. You will have to return to the dungeon another way, one that accesses the rear gate that you have opened. (see the related question)
You can't open the front of the cell. You have to go in the back way. Throw the switch in the dungeon and then go back out. You can enter from the tunnel to Mordred's secret underground lab. (see the related question)