1. Can you get high in your dream, if you have never experienced getting high? (as in meaning drugs and alcohol)

During a Lucid Dream your mind simulates experiences you have had before. This is what makes dreams sometimes feel so realistic.
With that being said, you are able to conjure any feeling during a LD. So yes

2. Are you able to watch a play or movie that you haven't seen before in your dream? Will your mind make it up for you, or will you be diverted from the screen at the last moment or something?

I assume if you try to watch a move that you haven't seen before your mind will make it up.

3. Is it possible to entirely control your DCs, or will they have a "mind" separate from your wishes?

With enough practice you can fully control your DCs. You just need to tell yourself that your are in full control and whatever you say they do.
As soon as you start believing it, the DCs will.

4. Is it possible to recall an old song, or an old book title that you've seen in real life, during your dream, and remember it until morning? I mean like old memories that you usually won't remember in real life.

Yes it is. Dreams are built on expectations and memory.


5. Is it possible to shapeshift your body in your dream?

Yes

6. Is it possible to change your point of view in the dream and still have control?

Again, yes.

7. Is it possible to extend the length of your dream? This is what I mean: a typical dream, no matter how long it seems like, lasts only about 20 minutes for the average person, because that's how long those particular stages of sleep are. Is it possible to make your dream as long as you want in your mind, and have it only last a few minutes in real life? I mean, it's your dream world right? Time doesn't really have much meaning.

ermm not sure what to say.
You cannot dilate time within a dream, but you can make it seem to go on longer. ie like a movie


8. Is it possible to kill yourself in your dream? Like, say you decide to stab yourself, for whatever reason. In a typical dream, you will wake up the moment before you die. Does the same apply to a lucid dream?

This varies from person to person. It is most likely what you expect to happen that will happen.
If you are convinced that you will wake when you die then you will.