What did the rakshasa use to study? Did they also have some kind of their own Veda? What did Ravana use to study?
I don't have enough reputation to comment but Ravana, in particular, was well-versed in the six shastras and the four Vedas. He is even known to be an excellent veena player. Therefore, we know that he was also trained in the arts.
- Prasad, B. A. "The Character of Ravana and Rama from the Buddhist Perspectives of the Ten Worlds." Language in India 11.5 (2011).
- Sanmugeswaran, Pathmanesan, Krishantha Fedricks, and Justin W. Henry. "Reclaiming Ravana in Sri Lanka: Ravana’s Sinhala Buddhist Apotheosis and Tamil Responses." South Asia: Journal of South Asian Studies 42.4 (2019): 796-812.
- Dirghangi, Aditi. "De-mythifying the Ramayana: A Study of the ‘Devoiced’Surpanakha." Proceeding of the International Conference on Arts and Humanities. Vol. 6. No. 1. 2019.