That's a lot of stuff, and to be honest, perhaps before you get deep into your Zelda game, you'd like to cut your teeth on something simpler. What you have up there is most of the game. The best way to learn is by trying, so either try them out and see what you can figure out, or do something simpler that uses similar features but isn't quite as complex. But anyways...
1. I helped you in your other topic.
2. I don't know what you mean by rooms (how to do them)
3. for random movements and attacks, you're going to be using a lot of if/then statements, and the random(num) statement a lot. If you don't know them, I suggest you read up on them in the help files.
4. You will need to create a controller object for this, one that will probably do a lot of the drawing by itself. functions such as draw_sprite, draw_text, etc. will be of great use to you. do some reading on those.
5. This can be included in either the collision object with the item, or at the end of the code where link opens the chest.
6. This one is difficult to explain, and most people do not try to make their own. You can try to find a dialog box online. I don't know what ones are good these days, but I'm sure that if you look in the engines forum or ask around, you'll find one.
7. After link falls in, put the line goto_room(room);. I'm not sure how your game positions link when he enters ar oom, but assuming that you want to go back to what entrance he was already in, since that's not changing anything, it should take you back to the entrance.
