Need some clarification on inspector scenes

As I don't know hindi, I couldn't understand the subplot involving Inspector Deshpande.

When Luke and Joy went to get the money from Nikhil's father (for kidnap drama) did Inspector found out Luke was the kidnapper?

If Deshpande already knew that Luke and the gang murdered Nikhil and his father and has the money, why didn't he arrest them, initially?

Can any one please shed a light on it...