I was able to complete the replacement without needing a new back glass cover. But I’d like to add a few observations:
1. The bottom side of my back glass was much more stubborn than usual, maybe it’s because my phone is 5 years old. No amount of heating and pulling revealed any opening on the bottom. But I was able to start the process on the right side instead. If the bottom side is too tough for you, maybe you can look around for other locations.
2. The black adhesive on my front display (what makes up the bezel on the top and bottom edges) started to peel when I was removing the midframe. I don’t know if this was avoidable, since it looked like the adhesive was stuck quite strongly to the midframe. The peeling is just a cosmetic blemish on the screen, but I heard that you can fix this by filling the peeled section with LOCA UV glue.