1. did the indians living before the muslim invasions establish great civilizations?

YES, before the Muslim invasion Indians established great civilizations such as Indus Valley Civilization, Mahajanapadas, and the Mauryan empire.

Explanation:

The Muslim invasion in India is started in the 12th century in India by the Afghanistan and Pakistan campaigns. Later the Muslim invasion was called "DELHI SULTANATES".Indus Valley Civilization is said to be the cradle of civilization because it was the first major civilization to be formed in South Asia. Later they spread in the North-Western parts of India throughout 3300-1300 BC.Indus Civilization is well known for its handicrafts, urban planning with grid patterns and well-facilitated drainage systems.