Just a few word class questions...?

Actually, if you are precise about it, a hole is neither an abstract noun nor a concrete noun. It's a hole. But the word "hole" is a concrete noun, which is a little strange, since it's a "concrete thing" whose primary claim to fame, in a way, is that it's not really there.

Actually, that's a bit of sophistry. The hole is definitely there. It's the stuff from which the hole was constructed that isn't really there. That by the way, is my proof fo the assertion that the word "hole" is indeed a concrete now.

If you navigated through that convoluted stream of consciousness, you're a pretty good paddler.