请教8老师，入籍oath waiver, proof of designated representative N648

请教8老师, I am applying for naturalization for my mom, who is a senior (73 yrs old),有老年痴呆. She has lived in the US as a permanent resident for more than 5 years. Her doctor already signed the N648 form (Medical Certification for Disability Exceptions)-waiver for the English and civics test. The doctor checked the box "applicant is unable to understand oath" in the 648 form.

1. to waive the oath requirement, USCIS will require a designated representative, is it correct ?

2. should i submit the proof for the designated representative at the beginning when we file it online (when we submit N400, N648 )?

3. or we do not have to submit proof of the designated representative at the beginning when we file it, and we can upload and submit it when USCIS issue RFE request for more evidence? if so, when USCIS issues RFE, will it cause a long delay? and when the evidence is submitted upon the request, the case will be re-queued for review (start all over again)? and will be reviewed by a different officer? 

4. What is the evidence/proof USCIS requires for a designated representative? (family member)

Thank you so much in advance for your time and help !