Sale agreement(Rs.100 Stamp) Validity

Hi, I have agreed to sale my land for Rs .7 Lakhs on contract basis irrespective of land size and written agreement by taking 2 lakhs. Unfortunately they have written in the agreement that i need to show the measurements while registration as per document. I asked about this before sign but they mentioned that this has been casually written and nothing to worry. Apart from that, They have mentioned in the agreement that within there months buyer need to pay pending amount and go for registration and if buyer fail to do this, they need to pay the interest to the seller. But validity of the agreement was not mentioned. I recorded the mediators discussions what was agreed initially. Due to delay in passbook processing, i could not register and i requested to pay some amount as i sold property on some need. They did not response for next 6 months after 3 months of agreement and now they are asking me the land for registration. As they have't paid the money on time, i don.t want to sell the land. Please suggest me.