levi reese

I have been playing with Minecraft forge 1.12.2 for about 2 weeks and have had many 1.12.2 mods on my server. I was wondering if I could still use 1.12.2 mods in a later version of forge like 1.14.3 but after installing that version of forge I soon realized I can't. Everything was fine until I tried to undo it, I was trying to delete the 1.14.3 forge and play on 1.12.2 again but it automatically deleted it when I downloaded a later version. I dont care about getting mods to work with 1.14.3 all I want to do is reinstall 1.12.2 but every time I try it says successfully installed and then in my installations it does not show up, I have even went further into my pc's files to try and delete 1.14.3 but it wont work. Anyone got any Idea what my problem is and how I can reinstall 1.12.2?