1: Ceiling light fixture edge definition:
-- use a large light cone down to make light energy instead.
-- place a small slab against the ceiling to stand in for your fixture with a material of constant reflectance on the top and bottom and plain white on the edges. For really fancy effects, use Emission.
2: Mirror: There's a mirror shader in the Surface definitions.
All this and more in the book. But you know that.
Dwight Atkinson