I will want to clarify first of all the words you used:
Demi-Gods : I don't know whom you call demi-gods, but in hinduism their is nothing like a demi god. Yet demi god's definition might look similar to the Devas. The son of devas in human form are not demi-gods, they might have some natural benefits yet they remain humans only.
Demons : There are no demons in Hindu Scriptures, there are Rakshas, but they are not demons. Demon means a being having supernatural benefits for wrong deeds, but nothing can go wrong against nature(leaving nature itself), so its not possible.
Angels : Even their are no angels in Hinduism, some people do try to comply them equal to Hindu Devas but their meaning doesn't fits in the definition.
Nagas : Naga are just humans, they are not of different origin or form, they are a very close worshipers of Lord Shiva, nothing else.
Divas : I never heard that word in scriptures, might be you looking for Devi. And Devi is the female attribute of Deva.
Rakshas : Among'st Lord's creations, their were animals with mind, amongst them were , Vanar( not a complete homo sapien, generally with monkey like attributes), Rakhasa and Humans. Humans are herbivore, and Rakshas are carnivore. This is only the structural difference. Rakshas have the same benefit which humans have, but due to their carnivorous nature they end up developing qualities(Extreme Rajo + Tamo gun) in them which is the cause of evil, hence most of Rakshasas were found evil in nature ( but not all).
In short in Hindusim there are Devas/Devis, Humans/Vanars,Rakshasas,Bhoot/Pret(Ghost) and other lower animals.
Among'st them the earthy minded animal ie. Human,Vanra and Rakshasa have a upper hand, they are give the power of KARMA. With their deeds they can not only challenge Devas but challenge god himself. Because of this they gain an additional benefit of gaining MOKSHA( the eternal silence, or the abode of GOD) for them, but others ie. Devas,Animals and Plants are restricted to assigned work and can only find MOKSHA while coming back to human form.