The largest part of the hoop at the top measures 5" across. The small end of the hook measures 2½" across. The largest part I could not measure a branch, so I measured the portion of my leg, just below the knee. It measured approximately 14 inches around. I hopes this helps you.
I would call your local store and ask a Sales Associate. I live in Arizona, and would not be able to verify current stock on hand. You can also order it online, and pick it up in the store within a few days, at no extra charge.
Yes, If you have a sturdy point/hanger for the hook.