Two questions from a beginner

Hi all, I've recently started tweaking around with reshade and just wanted to improve my understanding of 2 things:

1. How can I tell if a shader uses / requires the depth buffer?
2. My understanding is that AmbientLight.fx allows light from bright pixels to bleed to surrounding ones, but what exactly does `AL_Adaptation` ("enables adaptation algorithm") do? I'm hoping for some intuition on why it might be desirable.

Thats it, thanks all.

Followup: I also can't figure out what the difference between Colorfulness.fx and Vibrance.fx is visually.