When changing from a Version, wich equal to or lower than 1.12.2, for example 1.8 to a newer version like 1.16, all the keybinds reset. Also the mouse sensitivity is slower, even though the number in options.txt is the same. Autojump does also get reset and keybinds for fabric mods too. I think, this is VERY annoying and it could maybe be fixed by creating two profiles and when the launcher starts, and then uses the Options for the corresponding version. I hope this gets fixed soon,
Monsbot
Downgrading like that is not supported, please use separate folders for older versions.