Trade in Logistics

I have seen many recent posts on this topic.  I want to trade in my iPhone X (perfect condition) for an iPhone 13 PRO.  I tested the check out process.  I selected my current phone for trade in.  I received a popup box with the $700  trade in value (potential - once they receive and exam it - which makes me nervous with the outsourcing to Hyla). Took screen shots. In the check out process it asked if I wanted to receive my trade in packaging with my new iPhone.  I have also seen postings here that people unknowingly returned their trade in in packaging meant for buyers remorse. If I ask for trade in  packaging - how am I assured I have received the correct trade in packaging components and address?  I have also a question on the preparation of my trade in.  I found this document: (https://forums.att.com/conversations/other-phones-devices/att-tradein-tips-to-return-your-old-device/5f4fc125917fbb6f425c7f53?page=1) 

My understanding is:

• Back up all data etc to the cloud (This was not in the link above but makes sense)
• Reset the phone to remove all of your data, text, and pictures, and passwords
• Remove the SIM card (How do you do this on an iPhone 10- or is it not relevant for that model?)
• Take pictures of your device, front to back
• Take a picture of the tracking number
• Return the device within the offer window. Not returning your device voids the AT&T Trade-In Offer.

I have also seem comment about the return of the phone to Hyla and the phone being "locked" , and I think I read this is related to having the Find My Phone Feature still enabled. Is that correct - what are the proper steps to be taken for this - or correct steps to be sure my phone is not locked ( or any other issue they might find with the trade in)

I also want to upgrade my son's iPhone XR to a iPhone 13 Pro Max and get the monthly credit only installment plan (effective after month 3 - provided my trade in is properly valued at the $700, received by Hyla, not locked......and what else??)

I am very nervous, and would appreciate any supportive actions so I "do this right". 

Thanks in advance.