I've been working on a large build within single player and switching between Optifine and forge 1.12-forge1.12-14.21.0.2362. Since the newest version of Optifine came out I wanted to start working in that profile to work on my build, problem is going back to thinking about forge I realized that its not on 12.2. came back here to download the latest forge and I'm still getting a message saying that if i attempt to load the world in an older version it could corrupt my world. Just not sure what to do from here since I'm not technical savvy and would need a "forge for dummies" book explanation. I've attached a couple pictures to maybe help explain what I'm talking about otherwise I do apologize in advance if I cant clarify future answers. ^^;

Generally what i do is i build in sections and use mods with forge to either schematic it or world edit it to complete the sections. However with this one i've been working on it for a good 2-3 weeks and and felt it would be easier to build it outside of forge profile first and then use forge profile to schematic it together so i can adjust the look as i'm putting it slowly together. Thank you for the help and I'll make back ups now since i was careless this time. 

You'll be fine as long as you don't have special mods installed.

To solve your issue, just install a 1.12.2 version of Forge....