NDA

Hello Sumanth,
National Defence Academy is the academy which provides pre-commissioning training to those selected to join Army, Navy or IAF. It's not an engineering college. I am attaching a link that will give you all the required information about different aspects of the NDA.
https://www-shiksha-com.cdn.ampproject.org/v/s/www.shiksha.com/exams/amp/nda?amp_js_v=a2&_gsa=1&usqp=mq331AQCCAE=#referrer=https://www.google.com&_tf=From %1$s&share=https://www.shiksha.com/exams/nda
Best wishes

Hello Vishnu,
As per my opinion, cured myopia person is not allowed to apply for the Air Force through NDA. For the detailed information, you can read the article, I'm providing the link below:
http://newvisionindia.com/lasik-and-indian-army-indian-navy-and-indian-airforce/ click here.

Hello Vishnu, As per my concerned cured myopia person is not allowed to apply for the Air Force through NDA. For the detailed information, you can read the article, I'm providing the link below:
http://newvisionindia.com/lasik-and-indian-army-indian-navy-and-indian-airforce/ click here.

In NDA written, it's nearly 300 marks out of 900 with at least 25% in each subject. And for SSB, it's 700 out of 1800.

Joining to any Indian Services requires test and exams to clear. They check the abilities of the candidates over through tests. I suggest you to prepare for the NDA exams and attempt it to get into Indian Army. I am sharing with you below link where you can find the eligibility, exams and how to join Indian Army. It can help you to prepare for it. https://www.google.com/url?sa=t&source=web&rct=j&url=http://joinindianarmy.nic.in/alpha/login.htm&ved=2ahUKEwjIj7nx_o3iAhXLqY8KHdIUCXMQiB0wAnoECAgQDA&usg=AOvVaw1svR9ul-YSXVnsqY2KwRPn.

Yes, any small step taken to improve yourself of course helps you in the future.
Good Luck!

There is no minimum cutoff in 12th standard for NDA exam. You just have to pass the exam and apply for NDA exam.

There is no minimum number of attempts. Until the age of 19, you can attempt infinitely.

Hi Kartik,
As you have scored well in both the papers, you will be definitely able to clear this written exam. But at the same time, you must know cut off vary every year.
Best of luck.