After Effect Expressions

In After Effect 

It is a question of creating two expressions in Action Script.
 1 - A script, an "expression" thus, which will drive a degree of orientation of certain objects. The objects are in a "C1" composition, and they must tilt slightly according to the height of a camera which is located in the MASTER. The C1 composition is itself in the MASTER. The higher the camera is goes up, the more the objects should tilt slightly in proportion. When she goes down, the more the object must find its initial inclination.
 2 - Another script; always in After; so also in action script a priori... It would be a question of managing the degree of opacity, or more simply the display of a whole series of objects (thus layers on the time line) or elements located in a compo, the compo "C1" for example. By changing a single value, or a single switch somewhere. You change only one parameter and all the objects disappear or become opaque ZERO%. Compo C1 is toujorus located in another compo that serves as MASTER. If possible, by changing a single value on a layer located in the MASTER, you can switch off or change the opacity of all the elements that follow this script in the C1, or C2, etc. composition. As required.