You have to have a machine that puts the old serial number on the new part so the phone recognizes it. It's called "parts pairing" and it's why Apple sucks. I have seen someone do it with an EEPROM reader/writer but I could not find one for purchase so you would need to go to an Apple-authorized repair tech to have your new parts reserialized.

I was able to get through the guide in both directions, but there are a few ways that the steps are pictured or worded that made reassembly confusing. I am still new to this as this is my first repair (I can't believe I started with such a challenging one!) so I am not sure what I am allowed to edit for the pictures and guide step text, so for now I have started by just leaving some comments on what did not make sense to me.

This step has a duplicate screw from step 66. When reassembling the phone by following the steps in reverse, it messes it all up because in order to put this 2.3mm screw in, you have to put in the cameras and the bar that holds them down, but then when you get to step 86 the flash can't go in because the camera went in too soon. So I think if we simply remove the 2.3mm screw removal from this step then disassembly and reassembly should work out okay.

This is already step 87. It has to come out before the 1.7mm Phillips on the right side of the silent button.

Is the battery just stuck in there with an adhesive layer then? iOpener heat-up should release it, yes? Thanks for the guide!

I have some feedback on this process, because as I went through it some of the screws it turns out had already been removed by that step, or the pictures did not make sense because for instance the logic board had already been removed. I will try to figure out how to offer edits to the steps. Thanks for putting this together! What an intense repair, and it's my first ever one attempted. We shall see if I am able to put it all back together. Speaking of putting it back together, is it supposed to just be a given that re-assembly is just "all these steps, but in reverse"?