First thing about the NDA 1 is that if you were born on February 13, 2008, you are eligible to take the NDA 1 exam and the whole NDA process is of 1 year so when you go for your ssb u need ur 12th passing certificate so if you get your result on time you are eligible for the post if selected. And can fill the form.

Second case is You can fill the form of NDA 1 Even if you don't get result which is just like dummy exam you can give the exam but you are not eligible for the post but the thing is you get experience from the exam for next attempt.

Good luck..