Absolutely unnecessary for removing the rear cover. Instead, remove the small plastic piece at the swivel base that was held by two 2.5mm screws (see previous step) and continue with the guide.
The screws (in orange) near the swivel base are shorter, 2.5mm. Also do not remove the screws (in red) on either side of the screen, it is unnecessary for removing the rear cover. See my comment on the next step.
The screw on the left side of this photo is shorter than the other two.
Removing the front panel is unnecessary for removing the top case. Just pull the panel forward 0.5cm to unhook the top case from the pins in the front panel, then slide it back into position temporarily while you work with the top. This avoids needing to unhook the speaker or otherwise damage front components.
This step is unnecessary and risks damaging the tiny SD card door switch. See my comment on step 14 above to avoid removing this part.
Do not remove the upper orange-labeled screw. Removing the SD card door is unnecessary and risks damaging the tiny switch that detects the door being closed. Instead, loosen the screw about 1 turn and slide the front plate forward.
Not on mine, the two orange-labeled screws were coarse threaded, but they are not the same length. The 0.5mm longer screw goes in the hole nearest the battery door.
5mm screw, in case you unnecessarily removed the shutter button screw in the next step and mixed them up.
The adhesive holding the “6D” badge can give some resistance, be careful as it is very close to the delicate speaker wire.
It is unnecessary to completely remove the rubber from the right side of the back panel - in the next step where you remove two screws, simply lift the top right corner for access.