I have not worked on a google pixel before but here’s what I found out from working on other phones:
# That shield probably doesn’t do anything, and I haven’t seen a screw that is conductive, I doubt the pixel has one
# Yes, but you won’t be able to see anything
# Usually phones boot loop if you don’t have a battery connected
# Logic board, battery, charging board (you could use the power button instead, although I did this on an iPhone 11 and it wouldn’t turn on)
# I have no idea, I have never used a multimeter