Integration points are In-Plane which is independent of the number of Layers through the thickness, which is in an orthogonal direction. You will still have 5 layers whether you use Reduced Integration or not.
Stress in the Middle layer is based on the In-Plane (also called Membrane) loads.
Stress in the Top and Bottom layers is based on the Bending loads vectorially added to the In-Plane loads. That means if the sheet has in-plane tension, and by bending has more tension on the top and less tension (or compression) on the bottom, then the stress is higher on the top than the bottom.