Yes.
No, but a pyramid is.
A pyramid, as well as any other solid figure bounded by plane polygons or faces, is a polyhedron.
Yes. A polyhedron is a geometric shape with flat surfaces and straight edges, so a a pyramid with a rectangular base qualifies as a polyhedron. It is however not a regular polyhedron, which would require all the faces to be the same shape and size. To change your pyramid to a regular polyhedron you'd have to turn it into a tetrahedron.
No. A pyramid is a polyhedron. Many pyramids are polyhedra.
Yes because it has many faces which is the meaning of a polyhedron
yea it is
Yes.
Yes.
Yes.
No, it cannot.
Yes, it is.