Registered Sale deed cancellation

1. I purchased a house plot and got it registered from developer and builder on 8.8.2018. 2. Land conversion was obtained at a later date by the former who sold that land to builder. 3. A request for venture layout approval was made to panchayat secretary by the former but not developer. It was forwarded to dtcp which is not approved till now. 4. The plot that was sold me lies in the land of former A, but the link document given to me indicates the former name as B. Sale deed with B is already registered before my purchase. 5. The developer only entered into an agreement with former A to buy his land but the deed is not yet registered. 6. I have all evidences for the description made. 7. I paid 17 lacks and 5.5lacs due. As per the sale deed the value is only 4.23 lacks. 8. I spent around 30000/- for registration. 9. I demanded the developer to pay me 17lacs+30000+20000 for 2 months interest on 17lacs and cancel the deed. 10. He has agreed for that but not doing any thing. 11. What should I do to get that amount and cancel the deed?.