I never try. But i saw someone said online that wearing sunglasses when you not wearing 3D movies will cause headaches. But if you not wearing 3D glasses when you watch 3D movies, it will cause significant strain on the eyes. So, 3D glasses itself is not bad for eyes. You shall wear it properly for the sake of your eye health.
Maybe. If you wear 3d glasses for fun, you may get a headache or tired eyes after a while. When you wear 3d glasses to view things in the foreground, it will cause eyes to converge. If you use 3d glasses to view distance, it will cause your eyes to separate. In this way, your eyes can easily get tired and then you may suffer blurry vision. In my opinion, 3d glasses are used to watch TV or a movie, you'd better not wear them for fun.
Yes, if you wear it for a long time. No matter how good the quality is, it will make your eyes feel tired. So I suggest you don't do that. Because we wear 3D glasses is for the 3D effect of movie, it is not very comfortable to wear 3D glasses. And 3D glasses are expensive. Maybe you can find some other interesting glasses to wear instead of 3D glasses.