a rectangle
Pyramid
cube There are a great many solid shapes that have only flat surfaces.
It is a cube or a cuboid
cylinder
a rectangle
Pyramid
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.
You are a square based pyramid
A sphere
5 flat surfaces.
cube There are a great many solid shapes that have only flat surfaces.
A cube
a cylinder
A pentagonal pyramid.
There are 5 flat surfaces.
It is a cube or a cuboid