I am assuming that the latest update had a grub update and hence going back a snapshot renders you unable to boot with a message like “452: out of range pointer” or something similar.
The fix for this is chrooting into your system and reinstalling grub.
Try to follow this tutorial:
And then hold off on updating and provide us with the update logs first.
cat /var/log/pacman.log | tb
This will give you a link post it here. Your system looks a pretty recent install so your logs shouldn’t be particularly big to require filtering.