Income tax capital gains

Assessee invested in underconstruction property worth Rs. 1 crore on 1/4/2007. He paid down payment of Rs.50 lacs on that date. And then paid the balance amount of Rs.50 lacs in instalments upto March 2015. The property received occupancy certificate on 1/4/15. The assessee now signs the sale deed with the builder and registers the deed in his name by paying stamp duty etc in June 2015. Now the assessee sells of the property in Aug 2015 for Rs.5 crore. 1.Compute capital gains. 2.What will be the date of Acquisition. 3.Whether answer will change if certificate of occupancy is received on 31/3/15. 4. Under which sections can assessee claim exemption if assessee is ready to invest in any eligible exemption. 5. Support your answer with relevant case laws with its decision .