Capital gain tax on old property if new property is bought

I own an apartment in Pune, Maharashtra. I am planning to buy another large size apartment in Pune only. I have shortlisted few apartments which are currently under construction and expected possession is 3 years from now (Jun'27).

Do I have to pay capital gain tax if I sell my old apartment after possession of new apartment (post Jun'27)? Is there in time limit within which I can sell my old apartment to avoid capital gain tax?