Requirements for phone to power on

My pixel repair isn't going according to plan, so I am troubleshooting.

1.) Can the phone power up without the shield above the logic board? Also, what about the screws. Do they serve any conductive/grounding purpose?

2.) Can the phone power up with no display?

3.) Can the phone power up with no battery? (I.e, USB cable only, and battery disconnected?)

4.) What components can the phone function without? (I.e, if I had to do a trial/error teardown, are any components essential to the phone powering up?)

5.) The logic board seems to have multimeter contact points. Can this be used for proper testing? (I have a multimeter)

Thank you in advance!!