Slackware only does long term stable releases but Slackware current is a rolling release that does not really feel like a rolling release because of how Slackware provides a full and complete system as the base system. I avoided Slackware current for years because I did not want to deal with the hassle of rolling release, but it is almost identical in experience to using the release.

> The xserver (x11 or what as its old name)

It was XFree86 until around mid 00s after which the X.org fork took over.

I actually got a lot of Linux knowledge from the Suse handbooks, but when I was still buying a box in the book store because of slow internet connection in the beginning of the 2000. For Linux content nowadays the Arch wiki is still one of my most used resources although I did not use Arch in years.