Land Sale agreement in Maharashtra

My friend made a sale agreement of his agri land for Rs 1,25,00,000/- in Aug 2017. it was an unregistered agreement on a stamp of Rs.100 and the period of performance was 12 months . Said property was mortgage to local bank. The 7/12 extract was carrying bank charge. The buyer could pay only 70,00,000/- in the performance period. and the period expired Aug 2018. Today 20 months have passed after the expiry of agreement. Now the buyer has issued legal notice through a lawyer that there was a bank charge on property, the buyer has mensioned in his notice that remaining money of 55,00,000/- is ready with him. And has asked to pay entire outstanding amount of loan and remove the charge. otherwise buyer will go to the court and get the sale transaction completed through court. Now my question is: Is the sale agreement valid 20 months after the expiry date and Has buyer legal remedy to buy of said land now. My friend wants to cancell the agreement, what is legal remedy.