Yes, you can purchase NHAI/REC/PFC/IRFC bond on or Before 30th September, 2020 to claim Exemption of Long term Capital Gain u/s 54EC up to 50 lakhs. Last date is 30th September, 2020 in your case...
All investment extended but all investment are not extended to same 30th September, 2020 1.Chapter VI-A under the heading “B" investment i.e 80C to 80U extended to 31st July, 2020 2. Section. 54 to 54G investment, extended to 30th September, 2020