If F(x)〓x.x and G(x)〓|x|, then both FoG and GoF are differentiable at x〓0 being equal to x.x (or x squared). But G(x) is not differentiable at x〓0. Does this contradict the chain rule requirements where both the functions must be differentiable at their respective domain points?
It doesn't contradict, because the condition in rule is sufficient, so if it's held the superposition will be differentiable. If it's not held, we can't definitely say something about the result it may be differentiable or may not, it depends on certain functions.