How hot to heat it? The heater cylinder thingie that ifixit sells heats up to about 150F in the microwave. That seems to be about the right temp. However, I have measured my phone to be at 140F when it is being fast-charged, which implies that could soften the adhesive enough to open.

For me the battery connector could not be aligned properly once the battery was positioned in place due to torsion on the battery cable. You must first position the connector so it is square with the connector in the phone, press it in, and only THEN move the battery into its final resting place. When I did it that way it was easy. With the battery already in place (but not yet fully stuck), it was impossible.

When I tried this, the adhesive stuck to the backing better than it did to the phone frame, and became tangled. I don’t see any way I could have prevented that.

Do not hold the glass as shown. I did that, and the glass cracked when I tried to pull the adhesive because the adhesive was on tight. Always keep the glass down on a flat surface so that you don’t apply any bending forces to it.