My battery came up pretty easily:

I heated the battery to around 60C (145F), then used a plastic prying tool and an old credit card and pushed them in to cut / seperate the glue. Then just pulled the battery up. Be aware of the display cable underneath and where it is (see picks below), but in my case it was fine.

For the replacement battery the existing black adhesive sticker things in the phone were enough (if yours come up stuck to the battery, pull them off and put them back into the phone), I just heated it up a bit again after inserting the new battery to reglue it back down.

I had a lot of trouble with this, and the trick that worked for me was to do something similar to Alexander Haase above (minus the suction cup, I couldn’t get my suction cup to stick well enough to pull up the glass enough for a gap).

The bottom left corner of the phone - at least on mine - seemed to have the biggest gap and be most the ameanable to prying open. I used a razor blade and pushed it in at the very corner (as close as you can to the aluminium, so that you don’t wreck the plastic band around the glass), then jimmied up the glass with the blade until there was a gap. I placed a plastic prying tool / guitar pick in the gap, and pushed it around the edges to seperate the clips.

The way I did this bit was to heat the glass up to around 70C (160F) with a hair dryer, then use a razor blade to get in under the glass, then used a playing card and pushed that along underneath the glass to seperate the glass from the body. I started with my razor blade at the curved edge of the glass on the side of the phone, rather than at the straight edge at the top as they show here, because it was a bit easier for me.

Nothing else in my toolkit had a fine enough edge to get in under that glass except for a razor blade. The gap is very small.

How I did it was to heat the plastic to around 65C (150F) with a hair dryer, then managed to get one of my metal prying tools in and under the edge to pull it up.