edit, i see the screws talked about in step 3. sorry.

my two main points were precisely under the rubber feet, they were surprisingly difficulty to dislodge.

the tight side panel clips make this a difficult procedure, so take care both disassembling and assembling, for example make sure the power button is aligned with the level components behind before you push to clip the front home, as misalignment can break or dislocate internal parts.

mine had a PH2 screw on the printer back thru the side panel into the aluminum serial plate/back, placed in the 2nd and third picture in the tab with a round screw hole and square locator hole. Critical clips were center back, center top and center bottom, and two points on the front.

i think mine was a pair of #2 Philips screws.

Performed procedure on 8GB memory, 1TB fusion disk "Retina 4K, 21.5-inch, 2019" with magnificent success (I don't know if the Fusion bit is accurate). I was worried about the screen breaking in step 23, but was lucky and careful. I didn't do a disk clone (i had a data backup), then in Recovery, i initialized the disk and installed across The Internet, then upgraded and using the handy drive enclosure and USB cable to restore Documents and Photos. Now the machine is so fast, it's snappy and responsive especially in Photos.

i think the cable nearest the case edge is held in by friction and can be gently pulled, maybe with fingernails or a spudger. The next cable is held by a wire lever clip as described above it unlocks so the cable can be removed. These cables are also fiddly to re-insert, I didn't get one of them home and had no display after power-up, so at the end, don't re-seal the screen until tested.

I was fretting that i would break my screen, it's really hard to see what is holding the screen in place and i was ready for it to snap the last 1/2 inch or 12mm of the glass I worked slowly and as you say, keep lifting and working it gently until you can see and cut the remaining adhesive.