Government & Defence Entrance Exam

SSB has nothing to do with you medical condition. If you have the quality, then you will be recommended then later, you medical board will decide whether you will join academy or not.

Right now, National Defense Academy is only for boys but you may get a chance in the future.

You need to apply for NDA in UPSC website. Fill up the application form and add preference to Air force. After that, when you get admit card you have to give entrance exam of NDA. If you shall pass, then you will got call letter from SSB. When you crack SSB, then you will be directed to medical test. If they declared you medically fit then you will get joining letter to NDA.
Best of luck.

If you completed your 12, then you can apply. But for applying for air Force or navy though NDA you need PCM in 12 as well!

You can apply to various entries of air Force, depending upon you educational qualification. For class 12th, you can apply for NDA Conducted by UPSC.
For graduate, you can apply for AFCAT conducted twice a year through online mode examination.
You can also apply for CDSE - Conducted by UPSC again through offline written exam. You can apply for NCC. Special entry if you were part of NCC in college days.

Right now, all you have to do is to know the basics of IAS examination, about it's pattern and syllabus. Watch as many preparation tutorial video you can watch and frame you mind for the upcoming journey of preparation. Later on, you know what are your + point and weak point going to be then just focus on it and do not forget to keep yourself updated about surrounding though newspaper and TV.

Yes. You are definitely eligible for IFS Exam conducted by UPSC. It may seem like an exam for Agriculture Students but other students in similar field can pursue this course too.

Yes. The candidates could be graduate in any related field and be eligible for IFS exam.

There are various ways and different procedures to join army. Each is quite different and has different eligibility criteria. You can refer to this page to know more about it in detail. https://www.shiksha.com/careers/army-officer-14.