Just letting you know that it is possible to downgrade and obtain Muck v1.2, v1.25, v1.26, v1.3 and possibly older/future versions [other than the three Update 1 versions on the beta program]. (You can do so using the manifests on SteamDB -> direct download from Steam) I'm not sure if this is intentional or might be removed, but this allows us to get all the beatable (released?) versions (and a few old releases). I didn't log on SteamDB, so I'm not sure if there are all the old version manifests. I'm also not sure if v1.21-v1.24 were ever released. (No manifest available)

i Didn't Find Older Versions

Crafterdark how do you do that exactly? I couldn't figure it out, the only code I see is 1.26 and it's private.

1. First you need to download Depot Downloader from here: https://github.com/SteamRE (Showing the whole github page so you can understand where this is from)

(If you don't believe this for the login part... the code is fully open source and if you go here: https://steamdb.info/faq/ ...even SteamDB encourages to use it and it does really work as intended as I'll show below)

2. Then you go here, which is Muck depot, https://steamdb.info/depot/1625451/manifests/ (the first 4 manifest are, as of now, "v1.3, v1.26, v1.25, v1.2", all the currently released beatable versions)

3. Now, if you follow Depot Downloader instructions (using your Steam account), you will be able to download all the Muck versions using the first four MANIFESTID available on the link just above. (you can also use the six previous one to get the older versions too)

[IMPORTANT: You need Microsoft Dotnet installed for Depot Downloader]

Here's an example of the code you must use to get version 1.3 (with a command line, after being in the folder path where Depot Downloader is located on your PC):

dotnet DepotDownloader.dll -app 1625450 -depot 1625451 -manifest 7100742807621446579 -username <yourSteamName> -password <yourSteamPassword>

(Maybe you don't even need to use the username/password parameters at all to download it... since it's a free game, I'll try this tomorrow...but either way you'll get the game files inside "depots" in the Depot Downloader folder)

4. Go in C:\Program Files (x86)\Steam\steamapps\common\Muck and, first delete all the files you see there, then move in the ones from "depots\1625451\BuildID" folder you downloaded before and that's it.

Side note: ONLY the latest 10 manifest (versions) of the game are shown on SteamDB if you don't login with an activated steam account... but the game is new, so there's no need for Any%/Full game until there will be 11+ minor/major releases... (unless you want to see if they have even older manifests of the game)