regarding capital gains

It shall depend on the kind of Joint development agreement which you have signed. As per present law it shall be taxable on receipt of completion certificate from MC / authority

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but some more explain

There are whole lot of issues. For the purposes of capital gains, cost of land, number of flats to be constructed, estimated cost of construction of each flat, whether the JDA is registered or not, consideration received at the time of signing of JDA are some of the other issues for working out CG and Year of its taxability.