Dear All
1. How come Lord Shiva is a brahmin if he dwells in the graveyard? (Is he SC/ST?)
Kind regards
As said in Purusha Suktam (Rig Veda), Purusha (the greatest Person) hosts the Matter (with 3 gunas) and Selfs(jivas +Karma) subtly before creation. The jivas take various forms(bodies of matter) according to karma.
Primal Creation(Prakruti) itself is said to possess tri-gunas. So, upanishads even compared or personified the trinity (Vishnu, Brahma, Shiva/Rudra) as the tri-gunas, sattva, tamas, rajas respectively.
If you read Bhagavad Gita, 18th chapter esp. verse 14 given as follows:
"Brahmanas, ksatriyas, vaisyas and sudras are distinguished by their qualities of work, in accordance with the modes of nature."
The varna/class is by birth, the body/matter is formed from the subtle elements (5 jnana, 5 karma indriyas or subtle senses and the mind) which again is three-fold based on the tri- gunas. So, our complete genetic make-up is decided at birth, based on past-karma. Every form has a mixture of tri-gunas, but by birth we are pre-dominantly one nature/guna. And the Varnas are just labels to define one's predominant nature.
You are right, Rudra was considered fiery and passionate, wearing skulls, deer skin and matted hair (meaning fervently yogic). Rudra was also symbolically associated with ego and red color (Rajas). We may see in puranas, Ravana, Hiranaya kasipu, etc meditated deeply on Rudra/Brahma to fight against Rama/Vishnu etc. Thus those Forms were prayed to achieve some material feats or other goals, whereas enlightenment/moksha would be attained by the worship of Vishnu avatars/Forms. One may find his in the Gita Quote 7:23 " Those who worship the devas, go to their planets , but My devotees ultimately reach My supreme planet (vaikuntam)." So, the Shiva's Nature is associate with latter varnas.
'Shiva' means auspiciousness, in Sankrit, names are verbal nouns. In Vishnu Sahasranama, and in all vedic texts/puranas, one may find that Vishnu is also addressed as Shiva, Hiranyagarbha(womb of creation), sambhu(origin),mahEsvara etc... Rudra was called as Lord Shiva, possibly during the Mahabharata/Krishna period, when Duryodana/Jarasanda(Magadha) had a support of the North-east regions (populated/migrated srilankan-yakshas/nagas/kashmiris) etc, and Krishna wanted to make amicable friendship with them [later Arjuna himself got lost in Shiva!]. Thus all eastern tantra/practices, different icons became Vedic Shiva's Pantheon. Kashi(Magadha) became the seat of poly-theism/diversity. Then, cholas brought this culture down south. Else, My guess, the earlier Brahmins wouldn't have encouraged non-vedic worship. Later, these tantras/agamas must have been defined as per vedic injunctions. Anyway, now, we do not know which one is vedic or not