Push up question

Hey, was hoping for some advice on the push up. Is it imperative that our shoulders touch the ground at the bottom of the push up? Or just our chest? I took a video of me doing two sets of two reps, the first rep of each set I touch my shoulders, and the second rep I touch just my chest. Can someone shed some light on which is correct, or if it even matters as long as you are touching your chest to the ground?

Thanks!

I also have been wondering about pelvic rotation. Should we posteriorly rotate our pelvis just enough to not let out lower back "sag" or should we go for full pelvic tilt?

I wouldn't over complicate it, chest to the ground is a minimum but I wouldn't force my shoulders to the ground, you'll naturally lose some protraction as you descend.

Just tense your glutes as hard as you can, this should keep you from sagging and give the correct amount of PPT.

Thanks Murray!