Hi Sunny

Its a great honor and pride to serve your nation as a uniformed personnel or a military man kudos to your choice. As you might be already aware that CDS OTA examination is for the recruitment for officers into Indian Army for Short Service Commission and thereafter you can get extension of 4 years and if you want to serve more then you can opt for permanent commission too.

Now considering you eligibility and attempts there is a good news that there are no number of fixed attempts for CDS examination and all you need to have is just your graduation and you age should not be less than 19 and more than 25 and you are good to go. CDS is conducted twice a year and if your current age as you mentioned here is almost 20 then you are eligible given you have a degree from UGC recognised university and there are no fixed attempts for CDS examination you can give it as many times you wish given you are not above 25.

I hope this answer helps and best of luck!!