Monodevelop being insane.

Not loading assemblies properly?
Errors showing where there shouldn’t be, not autocompleting, etc.

Have you tried restarting Monodevelop? If so, then you could try quitting Monodevelop, saving your Unity project and then try loading the scripts again.

nope. But i just found out that the problem was in my framework NET. 3.5, it was accidentally turned off. you can check it in here. you can turn on your framework in this 2 video, it works for me. hope that help