I am unable to launch versions of minecraft that aren't vanilla; for example forge or optifine ect.

I know this is not directly to due with minecraft but the launcher doesn't seem to launch versions that aren't Vanilla. For example when I try to Launch a version of Forge or optifine an error message with pop up and say "The version you are trying to play inherits properties from an unknown version." I feel like this may be a bug because this wasn't an issue for previous launchers but if it isn't I can see why. There are people who will use and exploit mods on servers to via x-ray for people bases or to get end game material in bulk quickly. Either way If I could be briefed on this situation it would bring closure to my mind because I have been trying to fix this issue for quite some time. Also I type the version of the launcher and it said it didn't exist, in the bottom left corner the version number reads "2.0.760," and the version number that i can chose from suggests that the launch has been updated should I uninstall and reinstall? Thank you for your time.