Regarding HRA

Refer section 10(13A) which provides as below
House Rent Allowance: Exempt least of following;
(1)excess rent paid over 10% of salary due for relevant period; or
(2)Mumbai, Chennai, Kolkata and Delhi:- 40% and other place 50% of salary due for relevant period; or
(3)Actual allowance received for relevant period.

Say, my Salary(Basic+DA)= 250000; 10%= 25000/-.
Rent Paid= Actual HRA of Rs. 24000/- that the employer deduct for Quarter + Additional Deduction of Rs. 1200/- (24000+1200=25200),

(1) Rent paid in excess of 10% of salary, i.e. 25200-25000= 200
(2) 40% of salary= 100000/-
(3)Actual allowance received for relevant period= 0 (as I am residing in a departmental quarter, They deduct the HRA)

As per section 10(13A), least among the above three is 0. So, there will be no exemption in my case, right??

Yes, as per your example exemption will be Nil

What about section 80GG ??

में सरकारी शिक्षक हूँ मुझे HRA नही मिलता है परंतु में मकान किराया चुकाता हूँ 3500 प्रति माह तथा मेरी कुल आय वार्षिक 533617 है तो मुझे क्या 80 जी जी के तहत छूट मिलेगी की नही ओर मिलेगी तो कितनी pls बताने का कष्ट करें आपका आभारी रहूंगा