To answer your first few questions, yes, you can control your own dreams. This is called Lucid Dreaming. It's actually pretty fun and I've done it on several occasions. Once while dreaming, I realized I had no pants on and panicked about it because I was in a very public place. I soon realized I was dreaming, and then willed my shirt to become longer and dress like, and it worked. Another example is that I can willingly make things happen in dreams that I've read are near impossible.

I read on this website once that creating a room within your dream, in which the light switch can turn the lights on and off, is impossible. This is supposedly because the brain can't comprehend such a complexity as creating a room with working light switches when dreaming lucidly. I have since then, been successfully able to turn on lights in rooms, when fully conscious of the fact that I am dreaming. I don't know if what I read was true and I'm just an exceptionally creative dreamer, or what the case may be.

I also sometimes find myself becoming fully conscious that I'm dreaming when I'm having a nightmare of sorts and proceed to slap myself until I wake up. It's a huge relief when I finally wake up and the nightmare is over.

If you'd like to have more lucid dreams, try keeping a dream journal. Just take a notebook, I find composition notebooks work best, and keep it beside your bed, or close by. Then, when you wake up, write down what you were dreaming in the notebook. This supposedly helps your mind to make a note to remember your dreams, and subsequently, it also helps to allow you to have more frequent lucid dreams as well.

Anyways, sorry for the long post. I hoped I helped you out somewhat!