No. Every effect is 3D procedural (object space), so it works on any mesh without UVs, without images and without seams. It also ignores unapplied object scale.

Yes. Edges are found on the mesh by a small Geometry Nodes modifier, so edge wear works in Cycles and EEVEE (in our tests the worn edge area differs by 0.5 percentage points between the two). Only the optional "Bevel Node" edge mode is Cycles only.

No. Your shader stays in place and the wear is mixed on top. Remove Wear restores nodes, links, material slots and modifiers exactly: in our tests the render after removing is identical to the original, pixel for pixel.

The wear lives in Blender nodes, so FBX/GLB exports don't carry it automatically. Bake the textures (for example with a baking add-on) if you need it outside Blender.

Real Damage subdivides the evaluated mesh to sculpt chips and dents. Lower "Detail" in the Real Damage panel, or untick Real Damage on background objects. Your original mesh data is never changed.

If several objects share one material, all of them get the wear. Tick "Unique Copy" to weather only the selected objects: they get their own copy of the material.