No. As long as the hole in the glass is not cut larger than specified in the instructions, the square frame is sufficient, but it should then be sealed to the window, e.g. using silicone sealant. Since the square casing is not much wider than the glass cut-out, the round glass cut-out is visible behind the square (i.e. between the outer and inner parts), but this is not a visual disadvantage in my opinion. If you still want to prevent this, you have to come up with something for the round cover.

Yes exactly, as far as I can remember it needs this one.