How to downgrade game in Steam(instruction)

[SVV]

Changelog discussion had a link to instruction how to downgrade games. But it is outdated and no longer works. You can't download old versions from Steam client anymore, so you will have to use third party software with your login and password. That is a big problem. If you can accept and play recent update just do it. But I never compromise. Not even in the face of Armageddon.
1. Get DepotDownloader
Go to https://github.com/SteamRE/DepotDownloader download last version and unpack it somewhere.
2. Get .NET runtime to run DepotDownloader
Go to https://dotnet.microsoft.com/download/dotnet/5.0 and download right runtime. If you don't know what runtime is right, download https://dotnet.microsoft.com/download/dotnet/thank-you/runtime-5.0.8-windows-x64-binaries and unpack it in same directory with DepotDownloader. dotnet.exe must be where DepotDownloader.dll is.
3. Get right version of game
Go to https://steamdb.info/depot/457141/manifests/ and select ManifestID from version that was before update. The problem is that I don't know date of that version. Recent versions have debug files or can't be downloaded because of errors, so they are not right. I used my psychic superpowers and they told me to use ManifestID=3950115360070662764 from 25 June 2021.
That was for Windows version, if you use Mac or Linux you need other depot and manifest, use https://steamdb.info/depot/457142/ for Mac or https://steamdb.info/depot/457143/ for Linux.
Now from directory with DepotDownloader execute command:
dotnet DepotDownloader.dll -app 457140 -depot 457141 -manifest 3950115360070662764 -username YOUR_STEAM_LOGIN -password YOUR_STEAM_PASSWORD
Replace depot 457141 with 457142 or 457143 if you download version not for Windows.
Replace manifest 3950115360070662764 if you download version not for Windows or don't trust my superpowers.
Replace YOUR_STEAM_LOGIN with your real login and YOUR_STEAM_PASSWORD with real password.
DepotDownloader most likely will tell you "This account is protected by Steam Guard. Please enter the authentication code sent to your email address:"
Enter code from email and you will get old game files in "depots\457141\7036323"
4. Replace all files in "PathToSteam\steamapps\common\OxygenNotIncluded" with files from "PathToDepotDownloader\depots\457141\7036323"
5. Launch game from Steam. You should see BUILD: CS-469300

As you can see there are a lot of possible problems during downgrading. And you can't load game if you saved it in newer version. So this instruction is for a brave ones who are ready to risk.

[ALCRD]

This method fills me with paranoia.

I want to get rid of the recent ONI update and make it playable again but this seems way too risky.

[SVV]

Hooray! Old version(469300) was published as beta branch. You no longer need this instruction to downgrade. From now on I will backup games from Steam directory for easier restoration in case of unwanted updates.

[Foxster]

I've found that the Steam beta branch old version isn't quite the same as pre-merge version. 

It has some things from Spaced Out and some mods don't work. 

[sakura_sk]

1 hour ago, Foxster said:

I've found that the Steam beta branch old version isn't quite the same as pre-merge version. 

You need to deactivate the DLC from steam in order to play in the "previous version 469300" branch (if the screen in the bug report below is what you are seeing)

 

[SamLogan]

Returning to the past :