Ok, annoying
And I imagine, the offline installers you can download using the GOG website are the ones corresponding to these five game versions?
Nope, they only offer a backup installer for 1.63. Which you then have to manually roll back.
Or via the GOG client:
You then have to configure your installation in GOG, turn off auto-updates, and manually roll back to one of the last 5 versions:
So again, if you wanna roll back to 1.61, before the age of the tech preview, now be the time chooms.