Government & Defence Entrance Exam

You can register at UPSC website though NDA protal.

After 12th, apply for NDA entry. After Graduation, apply for AFCAT CDSE, NCC entries.

First, you have to complete you graduation and only you can apply for entries like AFCAT CDSE, NCC special entry, JAC entry etc.

It depends upon the entry for which you are applying for . Moreover 90% is good score to be eligible for all entries but do check whether the entry contain written exam or not.

Written is for both girls and boys.

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.