iPhone 6 Battery
I would definitely crack it back open and check the connectors. Could be the display unit but it's worth checking for sure. Good luck.
MacBook Pro (Retina, 13-inch, Mid 2014)
I don't know if yours would be the same but one thing to consider is if you don't plan on keeping the screwdriver/bit then maybe go with the T8 to be safe. It will turn the T9 screw, just not a perfect fit. I don't think it would strip it so long as you're careful. It's a pretty solid screw and torx aren't prone to stripping.
With my "A-stock" display there was no adhesive on the camera cable. It wasn't a problem though, because there was some slight adhesive left on the fan shroud from the original cable I pulled off. Doesn't seem to get in the way of anything either way, just lets Apple keep things tidy.
Guide was great, fixing my display was easy.
That said, the screws in steps 15 and 16 were T9 for me, not T8. Not great if someone buys just the tools they need, and not a kit like I did. (Kit's fantastically amazing, by the way!)
Main bummer: bought an "A-stock" display from iFixit and it has a 5 inch scratch on the back. Still works but I would have expected that to be B-stock.