class 102-- create a class with 3 different function

It would be a performance killer to add an event listener to each button.  It seems that you have 3 different types of buttons, and you want to assign a different handler for each type of button.

You could handle this with a single listener.

Mouse events bubble to the parent DisplayObjectContainer, and their parents, etc.  So you could just add a single listener to the highest common parent of the buttons (i.e. their "shared container"). The "target" property of the event will tell you which button was clicked, and can simply check which type of button was clicked to forward the event to the proper handler (e.g. over1, over2, or over3).  Make sure the mouseChildren property of each of your buttons is set to false, so that child objects inside each button cannot become the target, and only the button itself will be mouse event target.

shared_container.addEventListener( MouseEvent.ROLL_OVER, rollOverHandler );
function rollOverHandler( e:MouseEvent ):void
{
     var clickedButton:Object = e.target; //target is object that received mouse event
     if (clickedButton is ButtonClassType1)
          over1( e ); //forward event to handler for button type 1
     else if (clickedButton is ButtonClassType2)
          over2( e ); //forward event to handler for button type 2
     else if (clickedButton is ButtonClassType3)
          over3( e ); //forward event to handler for button type 3
}

If you set up your button as a SimpleButton (by setting its symbol type to Button), you don't need MOUSE_OVER handlers.

you could create one button class that contain 3 different rollovers and make your buttons class members.