a) what are you using the hdri on? ( I assume the construct but want to be sure )

b) turn off visible in raytrace ( properties tab ) on the hdri object - add a skydome to the scene and make it is not visible in camera ( properties tab ) but ensure that visible in raytrace is on. Copy your hdri to this dome.

c) sorry can't help here.

d) Save this script anywhere you like and run it to turn all lights off / on

# -*- coding: utf-8 -*- 

import poser

scene = poser.Scene()
for light in scene.Lights():
    light.SetLightOn(0) if light.LightOn() else light.SetLightOn(1)
scene.DrawAll()

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