SO I have this question:
I think the question is asking me to do a a partial differentiation to find dx/ds, dy/ds, dz/ds which I have found in my solution, but I am not confident with the approach I took to solve this question. My solution for those are as following:
Can someone please tell me if I am on the right path and secondly the question asks to find df/ds which I am not sure how to find.
As Kevin said, apply the chain rule to $\phi(s) = f(x(s), y(s), z(s))$:
$\frac{d \phi}{ds}(x(s), y(s), z(s)) = \frac{\partial f}{\partial x}(x(s), y(s), z(s)) \frac{dx}{ds}(s) + \ldots$