change of place of birth to London in Indian passport

[Vroom]

Hi
I need to get my place of birth changed in Indian passport from Delhi to London as my birth is registered in UK and I am adopted in India. My first passport was British but same was never renewed as i was adopted in India (with all legal formalities). By mistake my adopted parents put my place of birth as Delhi instead of London. Now I want to apply for British citizenship as I was born there to British parents.

Few queries :
1. Am I eligible for British citizenship ?
2. If yes, then before applying to BC, should I get my Indian passport sorted (place of birth)? What would b the process of same ?
3. What all docs to I need to submit for applying for BC?

Thanks