yes if they do something horrible like killing someone
Throw your spouse to the sharks. (that was a joke)
you wont open the gate from mordens gate to the dungon.
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)
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 a pokeball when he is on full health. i know it sounds wierd but it works.
throw a sleep seed at him and just pound him with power attacks
When you enter the dungeon from the library, and get the cheese, you should throw the switch on the wall. It opens the small back gate to the dungeon, from which a passage extends to Mordred's underground laboratory. Although you cannot return to the dungeon through the library anymore (its guarded), you can come in the "back way". (see related question)
Yes. Now, you can't throw the Grimy Food to cause damage.
it's a tradition
Once you get the gold coin from the fountain, and find the Library Slip in Mordred's Museum, you can access the secret stairway in the castle library. Click the McM shelf on the lower, Non-fiction aisle. In the dungeon, get the cheese and throw the switch that opens the rear gate of the dungeon cell.
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)
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)