Hi I purchased this several years ago. They are unopened masks however they are several years old. I would not hesitate to purchase the mask. What I would do is make sure that it is not dry rotted or cracked in any way. The best thing to do is test your mask by putting your hand over the inlet and breathing in if you do not have any leaks the mask is safe to use in a crisis situation. Most masks typically have a 20 year shelf life. The production date is usually stamped somewhere inside the mask. Check that and if it is within the 20 year mark you should be safe if it is older than the 20 year mark do the air seal test. Hope this helps.
It leeches through your skin, though, so you won't be protected. Even if you had a full body suit, you'd need a way to decontaminate when you were ready to take the suit off. On top of that, these filters are expired by some years so you'll need to hunt down a source for new ones. There's a date on the side of the filter to know for sure. They last about 10 years. Mine is stamped for 1995 so it expired 8 years ago.
They don't. U would need contact. No masks work with glasses because of how they have to seal around your face. I believe there are a few companies that make one you can put prescriptions in but are expensive.