Service tax for flat which was under construction, still not complete, going for registration

Hi,

During the registry of my flat which I purchased in a small project in Kolkata, I am asked to pay service tax of 3.6 percent of the total deed value. Total deed value includes car parking charge. Overall the project is still yet to be completed and even the building in which I have my apartment, is still under construction. The project overall has pending work for gate, boundary walls and all other amenities like hall, gym, lifts... I have the below queries:
1) How much service tax I am liable to pay as buyer of the flat? Is it on the whole amount of the flat and parking?
2) When I should get the completion certificate? Is there any authority who monitors issuance of completion certificates?
3) When is it that I should get my possession letter?

Appreciate guidance around these queries please.