Can builder keep ownership of common areas after sale deed?

The seller is not handing over ownership of common areas such as approach roads, the plot on which STP is present, the STP, relaxation garden. The sale deed says this explicitly that owner owns this and says we have usage rights, however, says the purchasers to form the association and maintain this. The seller has collected certain amount as upfront maintenance. This amount if put in FD, the interest can run the maintenance for a year. This is not mentioned in sale deed. The sale deed says the association to pay for maintenance. However, there is separate agreement with the seller for maintenance which might have these details. I am yet to see this agreement and its details. If the Phase 2 is later developed, how would the maintenance be later split if we, the residents have owned this up until then? What exclusive rights we have over these common areas?