But the context for the question I was thinking of didn't have anything to do with masquerades; I was thinking of the person being asked if they are the exact same person as the one doing the asking, which is impossible. Unless they are the future/past selves of each other, but that hasn't happened yet.
Even if others have such technology, such as the world in the future or aliens, the future and aliens haven't contacted us yet, so there's still no proof such technology exists.
Even with clones, answering "yes" is kind of iffy. The clone may have the exact same genes and face as you, but are they really, as a person, the same as the one they were cloned from? Identical twins have the same genes, but obviously they are not the same people.
But, uh, this is delving into stuff that's way too philosophical for me, so I won't go any deeper. XD