Downgrade version with steam but keep current install? (RO) (NOT a bug, Just asking for help)

[Hyperspace Industries]

I want to get an instance of ksp of version 1.10.1 (want to make a ro/rss instance) but I want to keep my normal 1.12.2 instance, what should I do? I know how to downgrade versions with steam (Carnasa's tutorial) and how to make separate instances. My problem is, how to keep my current main 1.12.2 instance, and get the ro/rss one too.  Any help would be greatly appreciated.  

[DeadJohn]

KSP has no copy protection so you can copy the entire install folder to a new folder. If you don't know where the folder is, right-click on KSP in Steam, then pick Properties (I think; not near my PC to check).

I always play from a copy folder, and if I'm changing mods in the middle of a playthrough I'll make a backup copy of my working KSP folder so it's easy to revert.

Steps like this should work for you:

1. Copy your main 1.12.2 KSP Steam install to a new folder named something like "C:\KSP_1_12_2\". The name can be anything you like but I recommend avoiding spaces.
2. Test that you can run KSP from that new folder and your saved game still works.
3. Use Steam to get whatever version of KSP is recommended for RO/RSS.
4. Copy the KSP Steam folder to another new folder like "C:\KSP_RO_RSS\".
5. Install RO/RSS into the folder from #4.

 

[jimmymcgoochie]

Yup, literally copy and paste your current 1.12.2 KSP from Steam’s folder tree (right click KSP in Steam library > browse local files will take you right to it) to somewhere else. Also ensure you’ve disabled Steam cloud sync as this can do bad things when switching versions and remember- don’t ever put mods in the Steam copy of KSP because it’s very likely to break your mods; the tech support (modded) forum is littered with people who’ve done that and then had their games mangled.

1.  Copy current 1.12.2 KSP, paste outside Steam (e.g. desktop) and that’ll be safe.
2. Delete everything out of Steam’s KSP GameData folder except the Squad (and SquadExpansion for DLCs) folders.
3. Switch versions (right click KSP > Properties > Betas > pick your version- on this topic, why 1.10.1 instead of .2? Is there something about 1.10.2 that’s worse?), then verify the files in Steam just to make sure it installed properly. Load that up at least to the main menu so you know that works.
4. Copy that 1.10.x out of Steam folders, paste elsewhere (could be desktop again but you’ll need to give them different names than “Kerbal Space Program” or it’ll overwrite the 1.12.2 copy, plus it’s easier to tell which is which) and then add your mods to this copy.
5. Leave the Steam copy without mods so it can get whatever updates the game will get, I expect there’ll be a 1.12.3 at least.