For the two functions
$$f\left( {x,y} \right) = {x^3} - 3x{y^2}\,\,$$ and $$\,\,g\left( {x,y} \right) = 3{x^2}y - {y^3}\,\,$$

Which one of the following options is correct?

The function $$f\left( x \right) = {x^2} = x + x + x + ....x$$ times, is defined

$$\,\mathop {Lim}\limits_{x \to 0} \left( {{{1 - \cos x} \over {{x^2}}}} \right)$$ is

At $$x=0,$$ the function $$f\left( x \right) = {x^3} + 1$$ has