These questions are all asked as if I am using a white black palette with all sprites having just those two colors. I think..... this question was already answered when filters were mentioned in another topic but I have never used filters before so I am not really sure what they do.
1. Can you use tweening effects to fade sprites in and out? During the tween effect things will have lots of different shades of grey. For example having a button hidden but then tweening in the transparency of the button to show that it has been unlocked.
2. Can you have sprites that stay in a faded effect to show some status? For example in a clicker type RPG you might have one monster with a 50% opacity to show it is stunned. Another example is a disabled sprite button to show that it is temporarily disabled.