Sold 3 Flats and Bought 1 Big Flat

Yes DEar Rishab,   He can take the benefit of Section 54 on the condition that all the 3 small flats were put to use for the residential purpose of the assessee.

Section 54 is clear in this aspect, provided the other conditions spelt out therin fulfilled.

s, mr.x can purchase a single property from the capital gains of 3 individual properties, the condition to be fulfilled is all the capital gains araising on the transfer of 3 capital assests should be invested.