UV flashlight like in Phasmaphobia

I have two tasks for my project that I don’t know how to implement. I am focusing on the game Phasmaphobia, it has a camera and a flashlight.
Task 1: Make a camera that can be held in your hands via RenderTarget, but how to display objects in this camera that will not be visible in the player’s camera?
Task 2. UV flashlight that illuminates objects that are not visible without it (ghost handprints).