First of great demo! II never thought I would see an adventure game in the form of zelda for 3dgs!
The good: The graphics and level design are very professional. Extremely nice models, textures, and lighting.
The bad: The gameplay is a bit too simple. It's just about getting keys with no real dangers in the way. Instead you need better obstacles and should think of a better way to open up new areas of the level like solving puzzles and being rewarded with a special weapon. The fire sword wasn't that good.
The ugly: The camera and movement need some work. The camera should be more free floating. The movement needs to be steamlined. Perhaps auto jumping should be looked at. The character controls too much like a tank instead of a person. The part that really needs work is the combat. There is no feeling of impact.

Otherwise, very nice work. Congrats!