I've used everything from Arch and Gentoo to fedora and Ubuntu. But I found myself enjoying the stability of Debian but hating the lack of newer packages. The latter of which isnt usually a problem when it comes to single purpose servers.
Yes and no. They seem to prioritize stability and security over everything else. So they usually only push updates to the stable repo if it doesn't compromise those 2 points (so new features are okay but so long as they don't create new instability or at the very least fix a security flaw).
So in other words nothing there is particularly ancient but most things are several versions behind just due to bugs being found etc. Great for servers but on a desktop most people wouldn't notice these kind of bugs so they tend to get pushed in other distro's a lot sooner.
They do get updated but very conservatively. They prioritize stability so their older kernel and system/library packages means all of their packages in general are also kept behind. Debian 11 for example is still on Python 3.9.2 whereas in Arch it's at 3.11.3 (and it's called python not python3).
I think so. They get freezed at some time on unstable (I think?). Then, if you need a newer (major version) of a package you need some other package source than the default Debian one to get it.