Advice required capital gain utilized towards buying a flat

Friends I want a clarification and advice on the Provisions of 54F of IT Rules, 1961.

there is a practical problem regarding this. My cousin has utilized the long term capital gain towards buying a flat. That capital gain was of 6 months earlier. The Flats possession will be given after 2 years. .till that time the time period mentioned u/s 54F will expire.

Now please answer how can i seek capital gain exemption u/s 54? What is essential in Tax Rules Investment or Possession. . Please reply as soon as possible.

Waiting for you replies !