Sale Deed Validity

Dear Sir I have agricultural land admeasuring 2.16 hectors. Out of which on 8.8.2017 I made a sale agreement for a piece of land of 59 Are. The agreement was made on a non judicial stamp of Rs 100. The agreement was not registered with registrar nor it was notarised. The total amount of Rs 1,23,90,000/- was fixed. Rs 30 lac was received as an advance amount against this sale agreement in the form of cash and cheque. The remaining amount of Rs 93,90,000/- was to be received upto 15.8.2018 (One year) in quarterly instalments. In the first quarter i.e. 31.12.2017 total amount of Rs 70 lac was received. There was a charge of Rs 50 Lac of a local cooperative bank on 7/12 extract of the said land however there was no mention of removing the charge in the sale agreement. After 31.12.2017 the buyer failed to pay remaining amount as scheduled. In the meanwhile we had repeatedly demanded him the remaining amount so that I could complete the transaction. Thereafter there was no any communication or transaction upto June 2020. Surprisingly the said buyer sent me legal notice dated 1.6.2020 through advocate for executing the said deed and completing the transaction. It is approximately 30 months after the date of execution of the deed. The notice was duly replied through our advocate and refused to complete the transaction as the stipulated period was expired for completion of the transaction. Accordingly the buyer filed a suit in civil court for performance of the transaction under sec 6 (six) of Specific relief act. In his plaint the buyer prayed for performance of transaction or to order to defendant to pay Rs 1.70 crore as compensation, if the performance of the transaction is not possible. In view of above my queries are as under. 1. The buyer has failed to pay the entire amount as scheduled in the stipulated period, he has served the legal notice after two years of the expiry date of agreement. Whether the notice is valid in the eyes of the law and the buyer is entitled to claim the performance of the transaction. 2. Whether the buyer can sue under the section 6 of Specific Relief Act as the said clause is not relevant to the performance of the transaction 3. The agreement was executed on a stamp of Rs 100, the agreement was not registered with the district registrar of the stamps, Nor it was notarised before any Notary Public advocate, the said agreement stamp was in the custody of the buyer, in such a case the agreement has any legal validity before law. 4. What is the remedy before me.