They are the plane surfaces which are bounded by edges of a solid object.
Coplanar means existing on the same plane. It is used in geometry to refer to points or shapes that all exist on one geometric plane.
The statement is false.
Yes it is. Anything that is 3D is usually a geometric solid. (Think)
A sphere is a geometric solid because it has 3 dimentions.
A plane is a flat surface
A cylinder is a geometric solid with two circular bases.