NDA

You can join NDA after qualifying the NDA exam conducted by UPSC. But Raw recruits its employees from different forces in India. That means Army, Police, CISF, etc. They do not release vacancies but instead see a person's potential and directly recruit him.

Yes, it is. Surely, you can understand why. Army personnel have to be at their physical best to survive the tough conditions they have to be aware of their surroundings all the time. Colour blindness may obscure your perception of the environment.

Study your class 12th science thoroughly. Read English Newspaper every day. Also, learn history through your coursebooks. There is no shortcut to success, remember this always and study hard.

If you are not more than 19.5 years old. Older than that will not be eligible.

NDA Exam is conducted by UPSC twice a year. You should be class 12th pass or appearing and less than 19 years of age. The syllabus of NDA is same as 12th Science and Maths. Also, you would need to make your English and GS strong. After you qualify the written exam, you will be called for SSB interview which is a 5-day interview that tests your personality and aptitude. If you qualify that too, you will give the medical and physical test. After that, you will be admitted to NDA.

Your eye power is quite low to be even qualified for Army Medical Test which is much more relaxable.
-6.5 means that you must habitually wear glasses and that may not be possible in Personal Training.

If and only when they are in same city and their timings don't conflict with each other. NDA exam is usually conducted in morning at around 10.

NDA is given by 12th passes candidates only. If you completed college, then you can appear for CDSE. The training through NDA is 4 years and through CDSE is 1.6 years.

The cutoff's trends depend upon the paper and changes every year. Generally, these are between 280-330 marks in the written exam and 20% marks in each paper.

You can appear for NDA exam after completing 12th and the syllabus is of 9th, 10th, 11th and 12th. There are separate books available to prepare for NDA. You can also join some coaching for better preparation.