Have you legally changed your name?
I have, yes.
Then the first you need to do is to inform Social Security so that they can give you a corrected card.
Can the Certificate of Citizenship be accepted as proof of US citizenship and what are the original documents I'll require??
Of course We can accept the following as evidence of US citizenship Certificate of citizenship N-560 / N-561
What do I do if you don't have one of these specific documents?
Do you have the Employee Identification Card?
yes
and the US Passport?
What if my document is expired?