Agreement of sale

Dear Sir, We had made an agreement of sale on (Rs.100 Non-Judicial paper) of land in Andra pradesh (we stay in Bangalore) on 21-OCt-2017. Till the time of agreement we were not aware that the person with whom were in contact is a broker, he himself said as purchaser. In the agreement of sale, the purchaser name is whom we never met. The broker had paid the 1/4th amount (in cash) of the deal on the day of agreement and remaining amount would be paid in 3 months and 10 days time. Broker made lots of promises before and now we are very uncomfortable with broker and his false promises and hence wants the agreement to be cancelled. Please provide us on how we can cancel the agreement of sale legally.. i will pay back the initial token and advance back to him.. 1- I know the broker bank acc no and branch, Can i pay back the money to his account ? But the issue is money in cash was given to me by the broker and not by the purchaser name in the agreement (i have not met the purchaser). 2- Can i send Cancellation of agreement notice ? Question is to whom i shud send? I cannot send to broker, i cannot send to purchaser (as i donno him) 3- What is the Validity of agreement? Is it 3 months and 10 days or any other fixed time ?? 4- Rs 100 Non-Judicial stamp paper is a registered copy or its a non-registered copy? Thanks, Nagaraj