Isn't there a way to download older versions of game on Steam? Or one just have to backup own games right after purchase, just in case?
I bet breaking a verified game on Steam Deck isn't even covered by basic consumer protection.
I assume you could look up the manifests in steamdb and manually rollback in any game? Monster Hunter Rise at least shows what I think are past versions https://steamdb.info/depot/1446781/manifests/
That said, presumably the older version is covered by the older DRM which may cease to work.