heptagon = 7 sided shape
There can be no such shape. If there were a shape with n flat surfaces, then if you sliced off one vertex, you would have a shape with n+1 flat surfaces. So it is always possible to add one more flat surface.
A shape with 7 sides.
a shape with 7 vertices
A sphere
It is a cube or a cuboid
A cube
a cylinder
A cylinder
A shape with seven edges is a polygon, more precisely it is called a heptagon.
7 is a number, not a shape in 2 or more dimensions. A number does not have a diameter.
a rectangle
It has 7 surfaces/faces