In the joint Developemnt Aggrement As a land owner how to take Flats posession

Hello , My fater had a Joint development aggrement with one of the builder in maharastra , this was a area sharing aggrement , where my father was a land owner has given the Plot for the development of appartment & in returns aggrement was done for Builder will give us 5 flats . After 2 years of delayes now finally the Property has receievd OC & now as a land owner i have few doughts. 1) In the JDA aggrement , flat Nos are mentioned alloted to us & completion ( OC ) has also recievd , now do we have to take possession from builder ( is it allotment deed or confirmation deep or possession receipt which deed is required) 2) if we want to seel those flats now to others do we to do tri partiate aggrement with the concern of uilder or we can sell with out the concern of builder. 3) in the earliest JDA aggrements , stamp duty was paid by the builder , Now as a land owner do we have to pay any stapduty if we want to retain 1 flat for us & 4 flats to sell off. Please do the needful.