No, a cube cannot have an octagonal cross-section.
It is a square.
Yes it can.
Yes, but not a regular one.
It will be the same shape as a square
Cube, Cuboid. Any prism with a quadrilateral cross section
Along any edge
a 2 +b2+c2=d2 a and b and c are length ,wideth and height and d is the cross section =D