Depending on which dimension you were speaking in perspective from... from a 3rd dimensional perspective, all two dimensional figures are "flat". (Meaning they have no depth or value along the 'Z'...
the empty figure
Yes, it's not 3 dimensional unless it is a box. Everything that is flat on paper is 2 dimensional.
two-dimensional shape (a shape in two spatial dimensions)
Yes, as it has length and width, which just happen to be equal.