It should be possible... but sadly enough it isn't.

Unfortunately not possible. There was this really annoying incident where WayForward patched a graphics glitch into River City Girls every time you do a Powerbomb. I wish i hadn't updated my offline installer because the previous version didn't have the glitch and they never patched it out again.

There is not. It has been raised, and completely ignored:
https://www.gog.com/forum/general/provide_a_full_and_complete_changelogged_download_system

Unfortunately these leaves some installers which do not work,or do not have the same content as before and no way to access them.

imho it is not needed , just make them work well on the os most gamers use atm win10

It's easy to rollback to previous version with Galaxy. There's no option to download older offline installers unfortunately. It's quite understandable in my opinion, because it would require huge server space to store them.

With Galaxy doesn´t require huge server space to store them then.

So aside from being more confirmation that offline installers are being deliberately degraded because of Galaxy (instead of complimenting them), what was the point of the "Galaxification" of offline installers during the installer structure change a while back (ie, the way the InnoSetup based installers used to store files directly but now store game files as a series of obfuscated Galaxy streams that gets reassembled into files), if they end up sharing no real-world advantage of that for end distribution?

My practical advice is flawed, but worth considering.

Essentially, one has to buy a game here they are interested in RIGHT AWAY after release. Download the offline installer (under "offline backup installers", though old folks like me who avoid the Galaxy client would call these "backups" the only installers worth having). Keep the offline installer saved on your computer.

Now, as updates trickle out, download the installers for them too, but maybe don't download every single one. Maybe only download once you can verify (typically through user comments on the GOG.com individual game forums) about any potential issues/unwanted changes. Don't get rid of the old installer/installers you have been saving.

This way, you will have multiple versions. I too wish there was a way to download whatever version I wanted...not every change is for the better. I suppose you could also try messaging Support, though I thought I read another user report that they might not provide the old versions anymore, since "just use Galaxy".

Iirc, in some cases GoG actually did - on-demand - provide links to older versions of the installers (like, for instance a build of Gothic 2 without the Night of the Raven expansion) in the past.
Might be worth a shot to contact support and ask if they happen to still have this older version of Control in their repository.

I honestly wouldn't bother. A few of us did that with the buggy Divinity Original Sin installer on advice of Larian, and the response was "just use Galaxy"...

Yes, but there is a difference in valuability of storage space. Galaxy customers are wanted, and thus valued more, offline is a nod to the past, and what they want to drop.

And it shows. Lately, every moderator message, from different moderators, had somehing that suggested in one way or another, that galaxy is good.

Yes, it has been noticeable that there is both an increase in moderator posting and bot account posting over the last month. Would lead someone to think that either the forums are dying (take out the forum games and then look), or that there is a big change on the horizon. Either way it’s not great. Ensure you back everything up offline.

If they pull the plug on the offline installers, man it is going to be ugly for them. The backlash would be huge. I don´t think they would do that. But still, lately I´ve been reflecting about starting to storage the games I value the most. To storage everygame I have I would need a hard disk of at least a terabyte. And that´s expensive. In a couple of months, perhaps. Will see.