Can I pay advance for property thru cheque without sale agreement

I the seller insisted advance of 5 lakh by cash but I disagreed and payed thru cheque transfer . He had given a word that he would sign the sale agreement once he comes to the property as my brother was his tenant for 7 yrs till nov 2019. From dec 2019 till feb end I have agreed to pay the rental which will be payed at the time of registration in March . The seller had come on 28 th feb to sign the sale agreement , he went thru the document and agreement and then asked me and mother to sign the first . We signed and then passed on the pen for him to sign . He signed the second page of the agreement and then immediately took his phone . He said excuse me and stepped out . Then came in and told me . U pay 10 lakh cash then I shall sign the agreement. I told him I have already mailed you the sale agreement and agreed to sign when u come down now why are u changing words . He said I am Govt employee I can’t sign for the full value , then I told him very clear that I do not any cash and if at all you insist any cash I will try at the time for sale deed registration . He then left and after 5 days he calls and says pay the rent . I told u have agreed for me to pay the time of registration. Then he gave him dates Like March 6th or 12 th to come down for registration Coz I felt something fishy about this guys behaviour . I borrowed money for interest and made all arrangements and he did not respond for the dates . Then my brother called him and asked him what’s his problem . He then said pay the rent then I shall come for registration after 10 days . He also told I am very disappointed that ur sister can’t arrange 10 lakh cash for me .