[mothered]

I would like to ask how the boxing method is carried out correctly that is to say it is not easy for me to get dry ice in my city

It can be purchased online.

the question I have is this: the spare iPhones I got are separated into two different orders, I want to know if it would be a return of 1 label or 2 labels?

Given you'll be boxing them, do the return on the one label.

since there are two iphones, the weight of the item is the following .932 kg (I leave you the photo of the scale), I imagine that I would have to put the same weight of dry ice, almost 1 kg, would this be prudent?

You're going by the shipping/gross weight, which Is not what you'll be working with.

It's the Item weight that's of relevance, thus the dry Ice will be based on that alone.

And if there are two return labels, wouldn't it be harder to believe that both boxes arrived empty?

That's why I suggested one return label.

Finally I would like to know if when closing the box pretending that it has been manipulated on the way, how much opening should I leave to allow the easy extraction of the smoke generated by the ice and if this could not raise suspicions when you meet the carrier?

It doesn't take much of an opening for dry Ice to sublimate when It's not stored In an airtight container, so keep the openings to a minimum.