Can light affect specific objects only? In C4D I can control which objects to affect with a light, in the image below only the main object is affected by the light source, the background and other objects are not affected. But I haven't found a way to do this in blender!

Is it possible to specify which objects to affect with a light source?
To remove specular, as that's the name for the thing pointed to, you select the faces that shouldn't have it and give them material of the same color, but with a different name. Then, in a node, set its Roughness to 1. This goes for Cycles.