rectangular prism
A rectangular dipyramid.
Yes.
Rectangular prism
A rectangular pyramid
rectangular prism
A rectangular dipyramid.
There is no such thing. A hexagon is a two dimensional figure. A three dimensional figure with six vertices is an octahedron.
a cube
Yes.
vertex or vertices
Rectangular prism
cuboid
A rectangular pyramid
There is not such thing as a three-dimensional triangle. You are thinking of a tetrahedron which is a three-dimensional figure with each side being a triangle. This has four vertices.
Rectangular Prism
The easiest way to think of vertices on a 3-dimensional object is to think of vertices as corners. Now, which 3-dimensional object has 8 corners? That would be a trapezoidal prism.