This is late, but yes, you absolutely can exit both Mumbai and Istanbul in the above situations, speaking from personal experience. Baggage will continue on your flights as usual, as long as the layover is under 24 hours, there is no need to pick up/recheck the bags. Any free hotel or tour (StopoverIstanbul or TourIstanbul) is only valid on Turkish Airways tickets, not on Indigo tickets starting with 3.