Stamp duty and registration amount for flat

Dear experts,

I have following questions w.r.t. buying of a flat in an under constrution apartments:

1) What is the stamp duty and registration fees as of today (i.e. january 2016) to be paid for registering the UDS of the flat?

2) What is the stamp duty and the registration fees to be paid for registering the construction agreement of the flat being bought by me?

3) In the sale deed of the UDS, can we mention the flat number and built up area of the flat being bought?

4) Should the construction agreement be registered first or  the sale deed of the UDS? Does the order of registration of the 2 documents matter? How do we link the document registration number of the construction agreement in the sale deed of the UDS and vice versa?

Please help me with these questions as i am planning to buy a flat.

Thanks in advance!