On Android I'm using Old Reddit Redirect. (I imagine just changing the URL is simpler, besides I'm not there enough to desire tons of features... I don't even have a Reddit acct. currently.)
On PC I just use old reddit boolmarks, and a bookmarklet that toggles to old Reddit :D
No, this one is on life support and it's the one which injects extra controls for image links, Twitter links and whatnot. The one you are thinking of is old Reddit redirect. And yeah, couldn't use Reddit without it
It won't allow reddit to have any tracking or analytics since no JS is able to run, it's practically a static html site. As for your experience, it works pretty much the same without JS