We currently provide user support for 1.14.4 and 1.15.2 versions of Forge, other versions should work (personally when I've seen people ask for help with them the answer is usually user error staring them in the face) but we won't provide assistance if they break.
Mods should only ever be installed by putting the jar file in the mods folder (inside .minecraft, look it up on the Minecraft wiki), if a mod tells you it needs anything more than that (barring putting other mods in the mods folder), be very suspicious.