Can u calrify me on capital gains query

Hi Friends,

         I need your help in this case - My Client is owner of the Land 550 sqyards and purchased in 1980 for 25000. Now this is given to Builder for development and getting 50%(50% includes 6residential flats + 10commercial flats) share and advance 300000

Questions: 

Applicability of CG Tax 

Construction Halt for 2 Years

Planning to buy Residential house with home loan and repay the money once above flats sold 

Wana to sell above flats

He has two sons and what is tax planning among three of them. 

Thanks,