As was said before: this is not true for an Arch Linux. You can choose when to update, but not what to update. It’s an all-or-nothing situation: you pacman -Syu or you don’t. There is no “update package X but not package Y”, because this would be a partial upgrade which is unsupported.
First of all: BTRFS is a file system, not a file format, but maybe that is what you mean. But what that person told you is a slightly wrong interpretation of what BTRFS snapshots really are. Don’t get me wrong: I also like the fact that I have them, but they are not always 100% reliable in terms of rolling back your system. I know because just recently, I went back to a former snapshot because I wanted to prove something (can’t find that thread now, though) and that completely killed my system. Could not boot anymore, was thrown into emergency mode instead.
So I booted from a Live ISO, chrooted into my system, did a pacman -Syu, sacrificed a baby goat on the altar of madness and luckily, I could boot again.
What I am saying is that having snapshots might still lead to problems when trying to restore them.
As others already said: this is a highly unusual request and I doubt that there is any automatism for that.
Let me ask you this: did you ever have something like that in Windows? And if not: why would you need it all of a sudden?
I am keeping diaries (== plain text files) of the things I tweak on my system, so I can look them up later. But they do not contain every single line of terminal output, that would be crazy.