Well, of course, you can wear 3d glasses with your prescription glasses. It is normal for many people to do this, so you should not worry about it. Also, you should know that 3d glasses are very popular in daily life. Definitely, they are more powerful than the regular glasses because of their special functions. As we know that the 3D effect relies on your two eyes each seeing a slightly different image, in which your brain then combines into a three dimensional picture. And also you should know that different 3D displays achieve this in different ways. Generally speaking, when you have worn a pair of 3d glasses while watching 3d movie, it will make you feel that you are just in the real phenomenon. This feeling just attracts many people. And also, if you wear prescription glasses and then have the 3d glasses over them, you can have good vision and feel the three-dimension at the same time.
Yes, of course you are allowed to wear 3d glasses even if you wear glasses or contact lenses, but it would not be convenient if you wear frame glasses. My advice for you is to replace your prescription glasses for a short time. Maybe a pair of contacts would be much more plausible in that case. However, there might emerge some dizzies feelings since you are not used to do this.
No, you cannot wear 3D glasses in this case. As you said, you have myopia, which means you can see the objects nearby in a clear way, but not the object far away. The 3D glasses are usually designed for 3D movies, which are made of polarized plastic, and they have vertical and horizontal glasses. The main usage of them are reducing glare to ease the eye strain. That is to say, it is useless for correcting vision, including nearsightedness. Therefore, when you are wearing 3D glasses to watch the 3D movie, you would have a blurry vision and may cause headache because of the glasses.