Mental Nuts-- Can You Crack 'em?

[ZenGum]

3. We arrange others into a perfect square.

Violating 10 makes it fairly easy. You could have a cube 4x4x4, having 64 blocks, and make a square 16 blocks each side around it, thus using 16x4 = 64 blocks, thus reaching HLJ's answer of 128. Or you could make the square double height, 8 blocks per side, and still use 64 blocks.

If we keep 10 but tinker with 3 and define a square as a line formed by one edge of a row of blocks, we get another option.

Think of a cube 4x4x4. Then wall this in with a ring 4 cubes on each side, i.e. leave the corners unfilled. Make the ring four blocks high. The square is the inside edge of the outer lines of blocks.