Downpatching Costume Quest 2

How to downpatch Costume Quest 2.

Launch Steam (Not in Offline Mode)
Press the Windows Key + R. This will open the Run window.
Open the Steam console by typing the following string: steam://open/console , Steam should now open in Console Mode.

Insert the string of the depot you wish to download and hit Enter. Below's example uses the oldest CQ2 Version for Windows.
download_depot 275180 275181 5372364152588491494

The first string of numbers is the App ID. The second is the Depot ID. And the last is the Manifest ID.
Feel free to find and change these numbers on your own via https://steamdb.info/

Steam will now download the depot. Note: There is no progress bar of the download in Steam, but it is still downloading in the background. You can confirm this by checking Steam's network usage in either the Downloads tab in Steam or via Task Manager. You can ignore any other information displayed in console. It is most likely unrelated to the downpatching process.

Return back to Steam console. Once the download is complete, it should say so along with the temporary local directory in which the depot has been stored. This is usually something like C:\Program Files (x86)\Steam\steamapps\content\app_XXXXXX\depot_XXXXXX. Before continuing back up this game folder.

If you don't have the latest version of Costume Quest 2 downloaded you will need that installed as well.

Now with both the latest version and the older depot/version you want to use. COPY all the files from your SteamLibrary\steamapps\common\CostumeQuest2 folder and PASTE them on TOP of the older version you downloaded. (C:\Program Files (x86)\Steam\steamapps\content\app_XXXXXX\depot_XXXXXX)

Make sure to follow the COPY and PASTE step above otherwise the older depot/version will just crash and not boot.

If followed successfully, you should be able to boot up the older depot/version perfectly fine. Feel free to delete the duplicate the game exe's. As long as you have this older depot/version as a backup in a separate folder it should never interfere with your currently installed Steam version. Enjoy.