I learned that i could separate mods by versions by creating a folder with the name of the version (like 1.8.9) and then putting the mod of the specific version in there, so after putting all the version folders, i tried to add optifine to the 1.16.1 folder, it all goes well i until i see that optifine wasnt installed, which i thought was weird, i checked if i put the wrong file in the folder or if i had typed the folder's name wrong but nope, everything was fine. I put a mod in the mod folder instead of the version mod folder to test if it worked and it did, I then realized that this was a beta so that's probably why it doesnt work, they just forgot to add that or theyre working on it. It could also be just that some people get a bug that wont let them do this or something, idk. If it is that they just forgot to add that feature, im hoping that people that work on newer versions remember to add this so they dont have to add it later on