You can do both post and get. That is all you need really to make anything work unless your are doing spyware and like graphical applications such as maps and what not.
Yeah but the point of "serverside rendering" is that you can just fill in the dynamic values serverside and serve plain html instead of needing a bunch of javascript and dom manipulation
Yes but a plain html file is static, so that's not going to work unless your site is purely static (i.e. a blog).