(a.) A slice parallel to the base would result in two rectangular prisms, as opposed to a cube now. These two rectangular prisms would be congruent to each other as it is a perfect slice through the middle.
(b) A slice that contains and AE and DH will make a slanted cube, meaning it will turn into a cubic pyramid.
(c.) A slice that will contain and vertex F will make the cut the figure in half going slanted. They will technically be congruent, although there is no name for this figure.