This is a really weird glitch. First off: occasionally when switching Minecraft versions, you will experience the tragic event of all of your saved toolbars just disappearing. This also happens with your controls. If your crouch key is set to Z, it'll automatically reset to Shift. Both of these bugs are so annoying and have been bugging me for a while. Please try and fix soon... thanks!
Downgrading is not supported. Use the launcher to set multiple directories for separate versions