The install script one hasn't aged particularly well. Although I haven't used the official one, so maybe it's not up to IRC standards. Everything else though, totally on point. When is this from?
Depends on the topic. Debian stable isn’t releasing software as things go on but instead update the package repositories to a version they deem stable. Minor things can change, but also if a big package update dropped on upstream and arch shipped it, some parameters can become deprecated etc.
Stick to your distro’s wiki/bbs/irc when possible, they exist for a reason ;)