The Buyer of a property has passed away due to covid. He had done the registration of property on the basis of agreement to sale while loan was under process . Now the buyer's heir doesn't want to buy the property. Will the amount be refunded by the developer or not?

If sale deed registration is not done then sale agreement(or the agreement to sell) amount can be refunded by the builder.  He may however demand for cancellation charges of around 1% but those charges can be negotiable based on builder. If the Sale deed registration is done then the buyer's family has to resale the property and give back the amount.