I'll answer no. 2.
Once you differentiate the equation of a curve set the the differentiated equation equal to zero and solve for x.
The two or more values of x are the stationary points.
Differentiate the equation once more and input these values of x into the new derivative (the 2nd derivative as it is known)
If the answer you get is greater than zero it is a minimum point
If the answer you get is less than zero it is a maximum point