It is precisely a square of siding to which each edge measures one foot. Therefore, each side of the square of siding is one foot in length.
Simply 100 square feet.
Cubic feet connot be expressed in square feet as they are dimensionally different. Cubic (think of a box) is 3 dimensional as in volume, where square (think of a piece of paper) is 2 dimensional as...
Not in this Universe, it's not.
One square yard is greater than one square foot.