Yes, 81 cubes can be arranged in a flat pattern of 9 columns of 9 cubes.
Yes, it can and it is.
4
27....
81 is einundachtzig in German.
8 square cm
quatre vingt-un
0.081
square
Cubes are prisms that have squares as bases and the height is the same as the edges. A square prism has square bases, top and bottom, and parallelograms as sides. A square pyramid has a square base and triangles for the vertical sides.
Three cubes.
A rectangular prism.
Cubes have a square on each side, but rectangular prisms have rectangles or squares.