It strikes me as one of the most fundamental topics imaginable on this site, but for whatever reason, there is no anatomy tag. Does this make sense to anyone?
It would very much depend on the question.
Most of the questions that I can think of off the top of my head that would fit the anatomy tag would probably be a better fit on Biology.SE. For example, your question about what determines whether a bellybutton is inner or outer, I don't consider to be on topic for health. What health impact would there be from knowing this? That (to me) is the defining characteristic of a health question.