A rectangular prism has congruent bases and parallelograms as lateral surfaces.
They are prisms.
It is called a prism.
In normal usage "polyhedron" refers to solids whose edges are straight lines, not curves, so a strict answer would be: there is no such polyhedron.
The bases of a prism or cylinder are congruent and parallel and they meet the lateral face (cynder) or faces (prism) at right angles. A cross section parallel to the longitudinal axis will, therefore, be a rectangle.
Not true. They have only one base and several (3 or more) lateral triangular faces. A pyramid has a single vertex over a base - there are no parallel faces in any pyramid.