@@Pixld_ Yes, but I'll need it again if the modpack gets an update. It's okay, though. I just use a virtualbox to download it. I don't run any antivirus to keep my system running smoothly, though maybe I'm just being overly cautious:D
It depends what mod you're using but in general you'll need to know how to .jar mod. There are videos for how to do that just search up "jar modding in multimc". The older versions don't have minecraft forge that you can use. Hope this helps!