It is given that \(f(x) = x\), a circle is enclosed by \(y = |f(x)| - 4\) and \(y = 4 - |f(x)|\).
Find the equation of the circle.
The line \(y = x\) meets the circle at \(A(a, a)\), where \(a < 0\).
Find the coordinates of \(A\).
Given that \(N\) is the lowest point on the circle, which is then reflected in the line \(y = x\) to point \(M\), find the difference between the areas of the circle and triangle \(AMN\), leaving your answer in the exact form.