The tv series from the early 2000s is a different timeline unconnected to the original movies, just sharing characters and setting. The more recent movies from a few years ago are prequels. Really you could watch in any order, but probably I’d recommend watching in order of release.

Probably a bad idea. If you really wanted to do it, you should add plug-in support to your main project, then create a separate repo, maybe under a different account, with the potentially illegal yts download plug-in. That way only the plug-in repo would get DMCAed and could be mirrored by other people, or hosted off GitHub.