Child ILR SET(O)

[Jay47]

Hi all

We will be applying for ILR for my son 9 years old next week. Me and my husband have ILR and are eligible for British Citizenship. I have 2.5 year old daughter. To outline this is our present situation:
1. 9 year old son born in India currently under Tier 1 general dependent. We are applying for his ILR under Set (O).
2. Me and husband under ILR and are applying for BC
3. My daughter born here and has no visa currently but we are applying for her naturalisation under MN1 section 1(3) along with our naturalisation (3 of us together)

My question is for my son with his Set(O) application as he will be applying as a separate application as the main applicant

Since he’s only 9 can we leave the section 2,3,4,5,9. Please confirm as we are confused wether to leave these sections as blank or to fill in my husbands infk as a sponsor.

Also kindly advise on what supporting docs we need to provide as we are applying postally.