In regards to all these questions

To be honest, I have no idea. Ifixit has students at Cal Poly write these guides, and I am one of these students. Students have to write the guides for a technical writing class, and ifixit uses these free guides from students who are trying to pass tech writing. Ifixit "pays" students by putting their name on the guide, and apparently letting us handle the questions, such as this one, that come up. The fixit guides are handy, but I won't be part of the system anymore.