Idle Up switch:
Idle Up in the off position is for take-off and normal flight. You should not turn the idle up switch on unless you know how to fly.
Idle Up in the on position is your aerobatic or 3d mode. Usually, this is a symetric throttle curve, meaning at full down on the collective, you're at full throttle so you can climb inverted. Then, in the mid stick, which would be 0 degrees of collective, you've still got plenty of power for doing tumbles.
This switch will let a second remote (plugged into your remote) take control of your aircraft so long as it's held. The moment you let go of the switch your remote is back in control. Usually, the instructor holds the remote that belongs to the flying aircraft and the student holds the extra remote.
This lets you reverse the responce the servo's move to the sticks. You would use this if right goes left or up goes down, etc...