Yes, I updated it then rebooted. Also made a thread on this issue, since it feels more appropriate.
sudo mv /etc/os-release.old /etc/os-release does nothing, sadly.
SOLVED! Thanks to @thefallenrat, I was able to fix the issue by chrooting into Live USB. Then I removed the
/var/run directory with
rm -rf /var/run in order to reinstall filesystem with
sudo pacman -S filesystem.
Thanks once again, mate!