Final answer:
The Svetambara sect is known for a liberal interpretation of Mahavira's teachings. The highest tier in the Indian caste system was occupied by the Brahmins. Ashoka was the Indian ruler who promoted the spread of Buddhism after converting to it.
Step-by-step explanation:
The Jain sect that interprets the teachings of Mahavira liberally is A. Svetambara. The Svetambara sect is known for its more liberal interpretation and is distinguished by the white clothes worn by its ascetics, in contrast to the Digambara sect, which interprets Mahavira's teachings more rigidly.
Moreover, regarding the Indian caste system, the group that occupied the highest tier is D. Brahman, known as Brahmins. As for the Indian ruler who promoted the spread of Buddhism after his conversion, it is D. Ashoka, who became a patron of Buddhism and helped to disseminate it throughout India and neighboring territories.