If you don't know the answer to question #1 someone may need to slap you. haha.

I'm relatively new to the internals of the ar 15. A simple app called gundisassembly can show you all these things if you are too lazy to pull out your ar-15. If you don't know these things already, purchase a stripped lower receiver and the learning experience you will get from it will help you more than we could or would... just remember, knowledge is power!