6) Why do teenagers feel the need to rebel against the rules or against other people (parents, teachers)?
I think that it is just a natural thing. The first reason is that we kind of come out of the shelter of our parents protecting. We find out about these new "bad" things and we get really excited. We get soaked in new ideas from our friends, older influences, and new media we are allowed to access. Then after we are saturated with these new ideas the teens ideals and the parents might not line up as perfectly as when we were eight. So we rebel and then comes the arguing and fighting etc.
The second part of it is teenagers finally feel like they can control their own life, but they still live in their parents house and under the parents rules so that creates a constant power struggle and the sheer annoyance that their parents still tell them what to do even though we know what is "best" simply cause teenagers to rebel more.