1. one thing i know for sure, you don't have to print the forms that don't apply to you.
2. if the area greys out (after you checked a box) , you leave the field blank.
N/A usually applies to other fields, for example when they ask you for your alternate names (aliases).. if you changed your name after your marriage and your passport name is your married name, then your alternate name would be your original birth name . you would write N/A only if you didn't change your name after marrying for example..
maybe more experienced users have more accurate info about it though.