Lease and sublease agreement of landed property

I am planning to book a flat to be built on a huge laded property in Mumbai. The title certificate mentioned that the owner (Govt. of Maharashtra) awarded certain FSI to the developer on terms that the developer is liable to develop the area,building residential quarters for Govt. staffs, building basic facilities/amenities for the residents etc. The owner has agreed to lease the FSI for 99 years @ Rs. 1 per year. For awarding the lease owner had invited bid and the the developer won the bid. It is admitted in the certificate that the agreement between owner and the developer is not sufficiently stamped and registered. In the same title certificate it is also mentioned that lease and sublease agreement has not been executed between the owner and the developer and should be done in due course of time. The developer has managed to receive IOD and CC up to plinth level. Now my question is whether there is any potential risk of booking flat in this project? Will the developer be able to complete the project after receiving all approvals? Is there any chance to change the lease terms such as increase of rent in future? How the cost of flat built on this land is compared with that built on a free hold land?