An Octagon
Octahedron
There is no specific name for such a shape.
octagon
square-based pyramid
an octagon
Octagon
An octagon
You take a look at what 2-D shape the face is, and then that's the name of the face.
One option would be hemidisc.
No. Every solid shape has at least one face. The closest you will get is a sphere, which has no edges or vertices, but it still has a face.
The geometric shape that has 1 square face and 4 triangular faces is a pyramid. A pyramid also has five vertices and eight edges. The square acts as the base for the shape on which it sits.
A triangle.