By technical definition, a compound word is a word made of a combination two smaller words. 'Were' is a word and 'wolf' is a word so putting the two smaller words together in 'werewolf' does, by definition, make it a compound word.
Yes, the word "werewolf" is a noun, a word for a creature in folklore; a word for a person (a thing?).
werewolves
Panther is not a compound word.
Yes, "kangaroo" is a compound word. It is formed by combining two words: "kanga" and "roo."
Yes, "cowbell" is a compound word formed by combining "cow" and "bell."