Juvenile Justice was really great, but it's hard to say why without getting into spoiler territory. Let's just put it down to overall character development.
Using a dedicated browser should be good enough. Since you might need some proprietary google stuff, I'd suggest chromium portable, that way once the class is over, you can simply delete the whole folder and call it a day.
On mobile I'd suggest Fennec instead of stock Firefox since you can use add-ons without limitation, and don't need workarounds such as the Firefox nightly.
It's basically stock with enabled add-ons, and following the official release cycle with 2-3 days delay. Maintained by the original developers of the F-Droid store, so also a highly trustworthy source IMHO.
You had to message LJ to add your email to the approved tester list... It's a pre-beta release with invitation only, not a public beta where everyone can apply. But it should be out soon anyway!
All of them. I'm browsing /all simply to block more, so that they won't accidentally show in my feed.