Capital Gain Tax

Deduction u/s 54F is available for purchase of flat.  I presume the land is not an agricultural one, in which case, deduction is available u/s 54B for purchase of another agricultural land. 

Regaring the doing up of interiors, this is an interesting query.  The cost of the house is normally reckoned to be what you pay to the builder or the previous owner and in case you specify all your requirements and the same is included in the cost, it will qualify for deduction.  On the other hand, after taking possession, whatever you spend may not qualify for deduction.