Kiranmayee

Juvenile House Sparrow? There's a light yellow gape at the base of the bill

I too think it is a Thick-billed green pigeon.. Beak looks like a young pigeon's..

Great pics.. But the tail and the whiskers near the beak look like a Drongo's.. Also the behaviour you described(acrobatics etc) point to a Drongo.. Could be Crow-billed Drongo, not sure, but definitely not a Crow or Koel..