Safest and easiest way to remove the bottom ring is rock a razor blade over each glued regions. Here are pics of all glued regions on a wireless mighty mouse

https://flic.kr/s/aHBqjBYvZe

Most difficult region for me was the bottom 2 glue points. But this likely will vary on every mouse.

I have pizza cutter. Cut top and sides no problem. Did 2x 21.5" without problem. 27" bottom long strip is the risky area. I have pro supply distributor tape + adhesive promotor + fully clean the tape surfaces so don't use glue / wrong tape. I put a safety fishing line on the 21.5 although that wasn't necessary judging by the fairly secured assembly. Maybe more necessary on the 21s.

And yes, I didn't dare to do heat with LCD diffuser sheets so nearby.

My note is just the bottom long strip on the 27". Didn't dare to tilt screen vertically after reading these comments and outlined my method to cut the bottom strip.

Really risky to crack the glass reading these comments. When I pulled the side tabs. one broke 1/2 way and the other tab just broke. Maybe because I had iMac laying on its back with the weight on it. Next time I'll try with it standing.

I lined a bunch of ultra thin cards to protect the bottom glass against aluminum frame while wiggling slightly. Make sure the cards are all the way to the edge (unlikely my pic) to protect that sharp corner. This help to protect the glass against the aluminum while I tilted slightly back and forth (~30 degrees max)

https://flic.kr/p/2qFgco9

Then I bent a small corner of the thin card, inserted from the edge and slowly cut across which probably cut about 1/3-1/2 of the tape width. Followed by a larger bend to cut it completely.

https://flic.kr/p/2qFgg9m

ISO to weaken the tape is possible IF you know where the microphone is to not damage that.

Super risky. If just want to replace the drive, much safer boot drive a USB3/USBC SSD

Are you sure there are 2 layers of tape? My replacement tape comes with the sections that sticks over the 2x antenna sections on the right side of the screen (looking at the screen). The old tape has antenna section left over because only the thinner edge part was cut so that section separated.

Furthermore, the replacement tape on the antenna section is only sticky on 1 side (facing the chassis) and no sticky surface to the screen (other than the thin 5-6mm width edge like the rest of the none antenna section.

As for falling off, I'm guessing there are 1. cheap tapes that looks the part but don't stick as well 2. surfaces not cleaned and primed 3) 2 top corner breathing channel (hot air rise and go out there) got sealed off as Step 6 below + pulling and stretching the tape sealed off that channel. Happened to me the first time, had to cut back to expose the air channel. On subsequent efforts, didn't pull to stretch the tape. Went gradually a couple of inches at a time so the tape don't stretch.

A few key notes

2 top corners have air gaps to let the hot air out. When applying the new tapes, its easy to stretch the tape and seal this hole using the method outlined below. Best to go slowly small section at a time to avoid stretching the tape. 2 people is helpful.

Before peeling the tape facing the LCD, its good to mount the LCD with masking tape (avoid covering mic holes) to test everything. I like to use Photo Booth and record a video to ensure camera and mics are all working properly.

2 people also helpful on the final reseal. I like to stand the iMac up vertically so can power on and do final check after LCD connection before reseal. The screen is pivots on the bottom edge and iMac chassis is wobbly on its stand so 2 people is helpful. For final check, I like to make sure screen powers on and display shows before final reseal.

I did not do this after reconnection. But read my post(10/8/24) on how to power up rMB after assembly. Need to use different smaller charger first before larger rMB charger. Also if didn't do this discharge step properly prior to disconnecting kbd/trackpad, they can fail likely due to corrupted firmware. I also show how to recover this situation in the post on 10/8/24.

This step is critical. If not done, there is a good chance trackpad and keyboard backlight will be dead on reassembly. If this, here is how to recover

Keyboard and trackpad not working after battery replacement

The LED light is quite dim so do it on a dark place to see it clearly.

After rMB is reassembled. CAN'T JUST PLUG IN THE USB-C CHARGER. Must follow an exact sequence with charnge with 1A brick first. See above link comment "Update 3"

The LCD screen is super soft on these since they rely on external glass for protection. Since LCD side will be facing down without disconnecting vsync, I'd lay it on a flat surface with soft fabric rather than putting the LCD on a rough surface like egg cartons.

Almost every vsync cable's 4 gold traces will be lifted after removal. Easy fix is to straighten them out, put some super/gorilla glue underneath. Clamp in a cloth pin for a little while and can be used again.

Lots of people lost keyboard + trackpad after this. Here is how I recovered it. Read through all the posts

Keyboard and trackpad not working after battery replacement