CPP Disability Backpay

I was told by my worker, i on on A.I.S.H. and i am fasd (born with disability) and was told months ago to apply for cppd but i didnt until a few months back as i didnt know what it was. i am wondering since i might have missed the date for working, i last worked a job with t4 5 years ago but it says you must work 3 years before application i think, and also since i was born with fasd will i get the full 11 months back pay ? i am 7 months since they sent the application will i at least get the 3 months if i am approved ? i have no insurance to pay up nor do i have any taxes i owe. sorry for the long post just trying to be specific. i hope this helps others with similar questions, thank you.