If you want mods to be playable in multiple versions get MultiMC or other third party launchers (that provide a separate instance for the version you want to play on) or move mods in and out of the mods folder (and use a 1.12.2 folder for mods on that version to load, but 1.13.2+ you can't have deeper folders) if your using the Mojang launcher.
Otherwise like TileEntity said it's not possible. The reason is Forge changes every so often and 1.13.2+ Forge was restructured which is why many 1.12.2 may not have updated or took so long (Tinker's Construct only just released for 1.16.5 and has been in development for 1.13.2+ during 1.14.4 but just wasn't finished enough even then). But there is no crosscompatibility mod for anything like that, sure CompatLayer was a think for 1.10.2 and 1.11.2 for some mods but that was a library for mods specific purposes nothing to a greater scale like Forge being basically rebuilt.
RLCraft is a modpack not a mod, and as it has 1.12.2 mods it's for that only. There is likely modpacks that try to do what RLCraft does but on newer versions just not all the same mods (maybe, you'd have to check).
For modpacks like RLCraft, you can use the Curseforge's aplication: https://curseforge.overwolf.com/
This aplication makes diferent instances (like MultiMC as SuntannedDuck2 recomended) with a single click.
Its maintarned by CurseForge team and connected to their webpage, so you can access to all the content published (mod, modpacks, texturepacks) and install them on one click.
I read carefoully your request and I think that this is not what you're looking for 🤔
I think that what're you looking for is to use features of 1.13 (like swiming & clear water vision) and 1.14 (like work station and new villager interface)