1. I-131 form's supporting letter, where should I get this letter, International office or HR?
-Not need any support letter.
2. My daughter is 10 years old, for her forms, should she sign or I sign for her?
-Yes, you can sign her name for her using this format: "your child's name/by parent: your name".
3. For the blanks that don't apply, should I leave them blank or I should write N/A?
-Leave it blank.
Thanks very much with all my heart!
