How were the States formed and how has the Indian map changed since 1947?

The story so far: On the “appointed day”, as Independence Day was referred to in the Indian Independence Act, 1947, British paramountcy lapsed in India, leading to the formation of two independent dominions- India and Pakistan. Pre-independence India consisted of state units, provinces and more than 550 scattered princely states. Nearly 114 of these, through the Instrument of Accession, had already joined India before August 15. The rest had the choice of joining either India or Pakistan, with most deciding to accede to the former.

From then to now, as India completes 79 years of independence and has 28 States and eight Union Territories, the internal boundaries of the country have undergone several changes with States being reorganised in multiple phases, with different factors behind the redrawing of the map.