Notice from buyer

My mother has a property in her name which she wanted to sell. One of our family friend approached and offered to buy the property in 36 lakhs. He prepared a sale agreement from my mother's side stating that a) she is in possession of the property. b) she wants to sell the property. c) she has revieved 10000 as advance. d) the buyer wants loan against this property and she is willing to recieve the loan amount. e) she will provide the documents requiered in the bank f) the buyer will pay the amount in six months and she will execute the sale deed g) she alongwith her legal heirs is bound for this sale agreement. The buyer , after two months offered to pay 24 lakhs as payment and rest after the sale deed, which my mother denied. Now, after ten months of this agreement, the buyer has sent a legal notice that she is not providing neccessary documents and refusing to sell the property. Is the agreement still valid and is she still bound to sell the property to him according to his conditions?