Social Orders: Shudra or Labor Class

                                                                  Q. 1. Also, if a man is born as sudra, is he not eligible to study the shastras, because the sudra's karma is to help all other varnas?

                                                                  As you stated in the initial premise of your question, one cannot be designated as sudra solely on the basis of birth, but by guna and karma.

                                                                  Q: In Varanashrama Dharma, are there any specific set of rules for each Social division (Brahmana, Kshatriya, Vaisya, Sudra) ? I understand that whatever the Social division is, they should work and live in Krsna Consciousness, But how Krsna Consciousness is differently applied to each of these division. For example a Brahmana Devotes His full time to Krsna, but other Divisions do their Professional Job and they will not have so much time as Brahmana to devote to Krsna. Also does the four Spiritual orders (Brahmacari, Grihastha, Vanaprastha, Sannyasa) apply to all Social Orders?