It won't be completely stable, when used without a case. The geometry is such that on the side of the lens it's the lens that is touching the surface where you put it, not the bar-shaped bump. Meaning, it won't sit on the long edge of the bar.
Yes, see for example the hands-on video of The Verge.
You can also tell from the side profile images on the Apple website. Drawing a straight line from the lens to the bottom edge of the phone doesn't cross or touch the edge of the "plateau", by a good bit.
I've got an iPhone XR with a chunky (highly protective) Speck Presidio case that's comfortably thicker than the camera protrusion and therefore lays 100% flat.
Gotta say it would drive me nuts to have a phone that didn't lay flat and couldn't therefore be put down safely on the edge of the sink etc.
It is really freaking obnoxious, I can attest to that. I think they either don't want to be mistaken for a Pixel for vanity reasons, or it's easier to do the magic camera switching if the 3 cameras are closer together. But for whatever reason, I hate not having the cameras in a row with a plateau that is symmetrical.
