Yes. A question that makes an assumption that something is true when it isn't.
For instance, "If computers were people then what would their favorite color be?"
The reason that it is a 'stupid' question is because it makes the assumption that computers are people, which they are not, and poses a hypothetical situation with a query that is in it's nature unanswerable. The only way to determine the answer would be if the original assumption of the question were factual, and since it is not the question cannot be answered.
Technically, yes. While the number two does not have a 'tangible' presence in our world it does exist in our collective consciousness, thereby allowing us to accomplish such things as measurement, sorting, and mathematics. If the number two did not exist then we would not be able to perform such feats without replacing it with another symbol of that number.
Hairbands are more effective, but style > effectiveness when it comes to fashion. My recommendation is to use a hairband/clip (a cheap one that won't break the bank) to see if it's worth giving up the band of lace for. If you find that it is worth it, then seek out a cuter hairband/clip to use.