Resolutions, frames per second - totally confused

This is going to be quite a lengthy question. Every piece of information is very cryptic and unsystematic.

So first of all, some background. I and some fellows companions are trying to make a series of semi-educational short films about a sport to popularize it and teach different aspects of it. That is why we have several sources of video inputs i.e. iPhone camera, GoPro and maybe some other cameras. And some of the performed elements have to be shot in slow motion for better comprehension (720p in 240 fps due to the limitations of these cameras).

And now the actual questions:

1) As far as I understand, the the first clip in the timeline will dictate the resolution of the whole project. So if I put a slow-mo peice the rest of the project will be in 720. But what will happen if I add this piece after an 1080p clip? Will it stretch or the whole project will shrink to 720p?

2) As the faq tells, if you put a 1080p 60fps clip in the beginning of the project, it will be rendered in 60fps, but what will happen to the rest of the footage, i.e. 720p slow-mo pieces, will they run in 60 fps as well? And another question arouses, what if I import video fragment from the GoPro? It only has 50 or 90 fps in 1080, how will it behave?

3) When I film a slow fragment on iPhone it automatically sets fast and slow parts and when i import this fragment, it appears on the timeline already modified, is it possible to import a "raw" version of it?

4) When I shoot a slow segment, it takes more light, and the light sources begin to flicker. Is there a guideline how to choose a special lamp for this kind of shooting so that it wouldn't flicker?

5) And a final question. If i do make a project in 60 fps, will it automatically upload it to Youtube in this format?

Phew, that's about it. I hope there are people that know this stuff and some of my questions will find their answers.