What happened to December puts which were purcashed as 75 lot, now it is 50 Lot ?

Has exchange given back money for 35 units of put which was purchased by me ?

All long-term Nifty contracts with a lot size of 75 will be reduced to 50 with effect from 25th June 2021. You can only square off your positions in multiples of 50 from 25th June. Any remaining position in the contract will be considered odd lots (not in multiples of the valid lot size). You will not be able to exit these odd lot positions, and these will be settled by the exchange at expiry.

From this article.