Can't reset pose position to rest position

Question 1: The difference between Pose position and Rest position remained after I tried to reset R/G/S with Alt+R/G/S. Why’s that?

Question 2: Please take a look at the 3 middle fingers of the left hand. As you would see, one of them behaves differently from the other two in the setup. Why’s that? Please help me.

Here’s blend. file:

When you clear rotation and location of the bones you still have the effect of the IK bone constraints (set their influence to zero to see the difference). When you enable ‘Rest Position’ the constraints are ignored

  1. So I fix that by rotate the displaced bone back to its place in pose mode and Ctrl + A to make it Rest pose. Is it ok?
    2. When I try to mirror the Left bones to the right arm by press S => X => -1. I got this problem

    The bones are not in a expected position. They are off so much.
    But when i change the chain length to 0 in the constraint from the pinkie finger. It goes normal. ???
    3. And what about question 2?