Fedora has something that resembles Arch as a rolling distro. Their unstable branch for development which they call Fedora Rawhide.
That said you wouldn't be wrong to call Arch a rolling release distro because it is one for the most part.
And besides, the behavior of Fedora Rawhide can easily be achieved in Arch Linux by just adding the [testing] repo that's already prepared (but commented out) in your /etc/pacman.conf
Indeed. However IMO this definition is not complete without taking into account the matching status of upstream software versions available and package versions made available by the distro at any given point in time. This is the continuous delivery expected and what gives a distro rolling status among its peers.
GNOME updates usually come when the packagers have time, latest this usually is the .1 release. 47 for example was available like a few days after the official release, if not a day or so after (I didn't check specific dates, but that was when I updated).
With other software it usually depends on if dependencies can work with the new version. LLVM is a major package that always is like 1 release behind due to stuff that depend on it not being updated for the new version. And shipping multiple of a single package is something they try to avoid.