NDA

Please refer this link
https://www-shiksha-com.cdn.ampproject.org/v/s/www.shiksha.com/exams/amp/nda/syllabus?amp_js_v=a2&_gsa=1&usqp=mq331AQCCAE=#referrer=https://www.google.com&_tf=From %1$s&share=https://www.shiksha.com/exams/nda/syllabus.

No,
Minimum qualification for appearing in NDA written exam is to pass class 12th with 60%. Do not try for graduate entries.

Hi, Please find the link below:
https://www.shiksha.com/exams/nda.

Yes, you can surely fill the NDA 1 form which is scheduled in the month of April 2019. The notification for this exam will be released in January month. So be ready and do go through the notification in which there would be all the details.

Yes, you can join NDA after completing your schooling form NIOS and from a recognised board with science stream.
Good luck.

According to your question, yes, definitely you will be allowed to appear for SSB and even to be selected for it as well. SSB has nothing to do with your medical condition, if you have qualities of an officer then you will get selected. Moreover once you clear SSB the task of checking your body well-being is with medical board. If they found any medical problem then you would be rejected. For checking the medical condition accepted, I advise you to Google it and see it from official site. They will provide you with all information.

Definitely, NDA is one among the best option after class 12th. Getting selected for NDA secure a job in the elite arm forces of India which is respected in and out of the country. Moreover, you live a life which not all get to have. You have perks of an officer.

For getting admission in NDA you have to appear for its written exam first. Moreover, for getting officer's post in army you can apply for TES entry of army which has direct entry and call up letter is based upon class 12th marks.

Once you are into NDA after successful completion of the three years course, you will be provided with a degree from JNU, Delhi and stipend during the course if I'm not wrong. Based on the wing you choose at the beginning, you will be sent to the corresponding academies after the three-year course. You will be offered a post of Lieutenant Rank after training.

Sorry, it's not possible.
NDA exam can only be taken by class 12th pass students, but if you want to go for army officer post then you can face exams like CDS, SSB, etc.