About that, a good example was Minoria:
If I remember correctly, one or two versions before the current one, there was a bug where a certain miniboss wouldn't spawn, and it was required for progressing in the story. While the devs didn't fix that bug, only people in the previous versions could play past that area.

Also, some games could receive retroactive updates, like NMS getting online DRM for certain parts of the gameplay.

And you could always want to check how the game was before certain updates.
I, for one, every now and then play in my Starbound Enraged Koala back up from Steam. It is quite a different experience, of which I enjoy.
And from what I was testing recently, it's no longer possible to make Steam download the beta versions of Starbound. (you could with commands before)

occasional reminder is good

Any suggestions to backup/restore offline games progress? (Paths, tools, portability, tips, etc)
Thanks in advance!

The bbc had an article on it today:
https://www.bbc.co.uk/news/business-58050387

Simply put, the more backups you can have the better. Online is ok as an addition to that, but anything you don’t have physical access to is not under your control.

For downloading GOG games, I use gogrepo. Not sure if it's the best tool around, but it does its job.
For Humble Bundle's Trove games, I've seen mentions of a tool similar to gogrepo, but I don't remember the name.
I don't remember any more storefronts with tools for downloading games more easily.

https://www.gog.com/forum/general/gogrepopy_python_script_for_regularly_backing_up_your_purchased_gog_collection_for_full_offline_e

Steam has one. It's called SteamCMD, but it's very primitive compared to gogrepo. Still, it allows one to download, install and play without the Steam client, which is important for me.

actually it does as it is extra download all the time they get updated and take a lot of space

I guess you are mainly referring to progress in a game, and perhaps never play a game long enough to complete it before moving onto something else for a while, before then coming back to the game at a later stage, and wanting to resume from where you left off. Plus of course have a backup in case something goes wrong ... hard drive dies etc.

The best advice I can give you, is to run your game from an external SSD you have installed to, that has a USB 3.O connection at least. Of course that is costly, but money well spent. You can even have more than one if you have a lot of games. That way you just plugin the drive needed to play the game. That's the simplest approach.

A better one, if you are cluey enough, is to run you game from an internal drive, and then offload it (move or copy) to another, and then back again at need. Of course, that is also best if SSD and a high speed connector, and some games despite that, are so large, they will still take an age to move back and forth. If you know a bit of scripting or can learn some, it is easy to automate most of it, as there is not much to it.

There is real expense involved though, as your game files could take up a lot of space, uncompressed, and SSD drives are not cheap.

Several mentioned in this thread, maybe one of them?

https://www.gog.com/forum/general/humble_version_of_gogrepo/page1

Found the name, "Trove Downloader": https://gitlab.com/silver_rust/trove_downloader