Cancellation deed for "agreement to sale"

Dear Experts, I wished to sell my house in Pune and in June 2015 I got a client. We agreed on a price of 1.23cr. In July first week they paid a token advance of 2 lacs with an assurance that they will pay the balance within 15 days. Then in Sep first week they came and we entered an Agreement to Sale and got it registered. The main clauses as given in the agreement are... 3A) The Purchaser shall pay the amount of Rs. 1,21,00,000/- (Rupees One Crore and Twenty One Lakhs only) by either a Demand Draft or RTGS within 60 days from the date of registration of present Agreement. After that the this Agreement to Sale shall be treated as a cancelled agreement, if the Purchaser fails to pay the said amount of 1,21,00,000/- (Rupees One Crore and Twenty One Lakhs only) within 60 days from the date of registration of present Agreement and the said Agreement to Sale shall not be binding on the Vendor. 3B) The Vendor shall then be free to deal with any third party purchaser of his choice in respect of the sale transaction of the said Unit / Row House. 3C) The payment of Rs. 1,21,00,000/- (Rupees One Crore and Twenty One Lakhs only) on within 60 days from the date of registration of present Agreement is the Essence of this Agreement to Sale. 3D) In case, the Purchaser fails to pay the amount of Rs. 1,21,00,000/- (Rupees One Crore and Twenty One Lakhs only) within 60 days from the date of registration of present Agreement, the Advance Amount of Rs. 2,00,000/- shall be forfeited by the Vendor. 3E) The Purchaser hereby agreed to Sign, Execute and Register the Cancellation Deed of the said Agreement to Sale after 31st October 2015, if the Purchaser fails to pay the amount of Rs. 1,21,00,000/- (Rupees One Crore and Twenty One Lakhs only) within 60 days from the date of registration of present Agreement. 3F) The Vendor shall not be liable to sign and execute the Sale Deed / Deed of Assignment or any other type of Deed or document after 60 days from the date of registration of present Agreement, if the Purchaser fails to pay the amount of Rs. 1,21,00,000/- (Rupees One Crore and Twenty One Lakhs only) within 60 days from the date of registration of present Agreement. 9) The Vendor shall sign and execute Sale Deed / Deed of Assignment/ Deed of Apartment or any deed or documents if and when required to be signed and executed so as to make the title of the Purchaser complete after receiving the balance consideration amount of Rs. 1,21,00,000/- (Rupees One Crore and Twenty One Lakhs only) Now as on date the buyers have not paid a SINGLE NAYA PAISA out of the balance 1.21 cr. It is clear that they are not able to arrange the margin money (15%) of around 25 lacs which is need by the banks to loan them the rest. They are not returning the Original Document of "Agreement to Sale" and are not coming forward to sign the Cancellation Deed. My question is... 1. Can I proceed ahead and sell this property to a new buyer without the cancellation deed? 2. How can I force (legally) the buyers to either payup or sign the cancellation deed? 3. Under which act/law can I file a legal suite on them for harassment since they neither want to pay nor return my documents nor sign the cancellation deed? I am also loosing good opprotunities with other genuine buyers Regards, Rayomand