Does "A couple of..." always means "2" or sometimes can be "3" or more?

A "couple" always means two things or people. If you ask for a couple of blueberries, it still means two, even if the person getting the berries gives you more than two. A "few" of something means more than two, but still a small number. "Several" means more than two or three, according to WordWeb, and usually means more than a "few". "Some" is another word that usually means much less than half of whatever you're talking about. In terms of quantity, "few" would mean less than "several", which in turn would mean less than "some". The word "few" is the only one of these that has comparative and superlative forms: "fewer" and "fewest".