The white sticker on the SIM Card Reader appears to be a water-damage indicator sticker.

I noticed mine turned slightly pink when I wiped it with a microfiber cloth that had a bit of isopropyl alcohol on it - trying to remove oily fingerprint residue before closing the phone up again. I will only use a dry cloth next time.

I kinda forgot about this step when I opened my first iPhone 12.
For the next one, I'm going to mark that edge of the phone with blue tape roughly where each cable is to help me remember.

Also FWIW, I got the 70 cent adhesive cutting tool from Apple with my genuine battery and used that for all my display prying needs after getting the first opening propped with a guitar pick.

It worked great and did not damage anything so no need to sweat inserting something too far and causing damage.

A very helpful addition to this guide (for me) would be the inclusion of a photo showing the iPhone with the battery fully removed, like this one in the official Apple repair guide.

I used the black spudger to nudge loose broken adhesive strips after adding 99% isopropyl alcohol, but I was not thinking about the wireless charging pad or the other cable running underneath the battery.

I accidentally pried up part of the charging pad cabling cover.

HIGHLY recommend not jabbing anything underneath the battery farther than a single guitar pick can reach.

I have not attempted wireless charging yet but honestly I prefer to avoid it whenever possible as the extra heat will degrade my new battery faster than wired charging.

The official Apple repair guide advises removing the adhesive tabs starting with the bottom right tab just above the loudspeaker - step 43 in this guide.

They also demonstrate this with a more pointed tweezer, which I would like to try next time.

My blunt iFixit Tweezer cannot grasp the pull tabs effectively - maybe mine are worn out or bent in some way I have not noticed.

I mostly had to use my super pointy, curved iFixit Tweezer (the middle one in this set) that has a tendency to cut thru the pull tabs when I don't want it to. But the right-angle curve really helps get into that tight space well, so it's kind of a balancing act to find what works.

Next time I plan to apply a few drops of 99% isopropyl alcohol to each pull tab a couple of minutes before pulling them. Ultimately that helped A LOT.

The official Apple repair guide does not recommend removing the SIM card reader or Taptic Engine.

Instead, after removing the loudspeaker it advises only removing the standoff screw on the right side of the Taptic Engine. Then proceed with removing the adhesive tabs, starting with the bottom right tab just above the loudspeaker - step 43 in this guide.

Lots of folks skip removing the SIM card reader and find it is much simpler to complete the battery replacement.

I removed mine and it did not help me since my pull tabs all broke off anyway, so I spent a lot of time fiddling with reassembly - especially the standoff screws.

The official Apple repair guide does not recommend removing the SIM card reader or Taptic Engine.

Instead, after removing the loudspeaker it advises only removing the standoff screw on the right side of the Taptic Engine. Then proceed with removing the adhesive tabs, starting with the bottom right tab just above the loudspeaker - step 43 in this guide.

Many folks commented in the iFixit YouTube video for iPhone 12 battery replacement that they did not need to remove the SIM reader or Taptic Engine to replace their battery successfully.

I always start with the temperature on the warm or low setting, then turn it up as needed. This helps avoid quickly overheating things, and recently worked fine when replacing the battery in my iPhone 12.

Hot/high probably could have saved me some time, but I wanted to play it safe the first time I opened this model.

I did find that a hairdryer was far more effective than my iOpener on the iPhone 12.

I've used both for various projects in the past, but this one definitely needed the extra heat available from the hairdryer.

The clip holding the LED ribbon cable to the motherboard is the most fragile (in my experience) and broke when I removed the cable.

The steps here do not show disconnecting it or the trackpad ribbon cable, but they are similar to the larger cables in that a grey plastic tab needs to be lifted before the cable is pulled - otherwise the cable can break.

I appreciate the guide, it was very helpful in removing a motherboard.

I was having major trouble with Bluetooth, and occasional trouble with WiFi.

I followed this guide to remove the WiFi card from my 2015 MBP and install one from a 2013 MBP.

It worked, I had to remove and re-add Bluetooth devices and they do work better but still not as consistent as they should.

While I no longer have typing lag on my Magic Keyboard, it does cut out when using AirPods that work fine with all other devices like a newer M2 Mac mini.

I do still get a frequent error that my Apple Watch signal is too weak to unlock the laptop.

I’m curious if I may have an antenna problem too, or if there’s something else I should try to improve bluetooth performance on my laptop.

Any suggestions are welcome.