Mutually agreed to cancel agreement of Sale, Seller is returning half token money, rest soon
I was interested in buying a 3BHK with agreed amount of ₹ 60L (deal was good economically), since the seller was in debt and wanted to sell off flat earliest, he demanded ₹30L as Down-payment and rest amount due when the bank approves the Home loan. We executed a sales agreement on just stamp papers and I did payment thru RTGS and have records,As a surety, I took all the original deeds in my possession when I paid the money. . Agreement was due to expire after 45days on 1St Oct 2021.
I tried multiple banks for home loan but due to some potential litigation issues, banks denied hoke loans and I informed the seller about the progress every time.
Meanwhile, Seller used up my money to pay off his debts. Now that I am no more interested in this deal citing multiple banks rejecting loan application, I requested for cancelation of deal and refund of my 30L.
Seller promised to pay off as soon as he finds any other buyer. He recently called up informing me that he found a new buyer and he shall give me 10L which he would get from New buyer as token amount. But he is insisting that I will have to return original documents to new buyer. He also promised to return rest 20L within a month as new buyer agreements states he shall pay off all amount within 30days.
Seller is promising me to sign an undertaking on ₹100 stamp paper as "Cancelation of sale agreement", state all the amount details, how much paid and due amount and 30days return time and offered me bank cheques of 20L as surety if I wish to have.
My question is, looking at the amount and to be on safer side, what can be done, the said cancelation of sale agreement + Cheques are enough to be safe or do I need to execute anything else to be safe legally?
Please advise at the earliest. Thank you so much in advance