What to do before selling an iPhone

I would start at: What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support

The 10 Most Basic Things

1. Back up all your data (iCloud or computer).
2. Sign out of iCloud and Apple ID.
3. Turn off Find My iPhone.
4. Erase all content and settings (factory reset).
5. Remove the SIM card and eSIM profile.
6. Unpair Apple Watch (if connected).
7. Sign out of iMessage and FaceTime.
8. Check for carrier lock status.
9. Clean the device physically and remove personal accessories.
10. Prepare original box, charger, and documents (if available).

MichaelNguyen88 wrote:

The 10 Most Basic Things

Back up all your data1.  (iCloud or computer).

2. Sign out of iCloud and Apple ID.

3. Turn off Find My iPhone.

Erase all content and settings1.  (factory reset).

2. Remove the SIM card and eSIM profile.

Unpair Apple Watch1.  (if connected).

2. Sign out of iMessage and FaceTime.

3. Check for carrier lock status.

Clean the device physically1.  and remove personal accessories.

Prepare original box, charger, and documents1.  (if available).

Your instructions cannot be carried out in that sequence. Even after your edit.

Think again