No, you should not reuse the costume contact lenses when they get out of the expired time. It is so dangerous to wear the expired contact lenses because the water content character in it is losing which may cause your eyes to be very dry and let your eyes get infection.
It depends on what costume contact lenses you buy. If the costume contact lenses are reusable one such as weekly or monthly, you can reuse it until they are expired. But if they are disposable contact lenses. you can only use it for once and then throw them away. You are not recommend to use such disposable costume contact lenses. It will ruin your eyes.
Well, it is true that nowadays there are more and more strange things emerging in the marketplace, maybe costume contacts is one of them. Generally speaking, they are designed to facilitate the performance or something like that. However, they are not going to be reused since the design and quality nature decided that they are not to be kept for a long time, so you'd better dispose of them properly after use.
No, you had better not to do that. As we all known, costume contact lenses is a kind of non-prescription lenses that are mainly used for special occasions like moive, opera. In general, this kind of lens are colorful except the center is clear due to it is used for decorating eyes, not for correcting visiion. The lenses are directly touching your retina, thus they are suitable for wearing for a certain of period. Otherwise, the color on the surface of lenses would cause eye infection or irritation. That is to say, the costume contact lenses are not suitable for repeating usage.