Hidden objects

Question

being new to actionscript3 I thought I would create a simple little game involving a skydiver who is supposed to be falling towards the ground, the problem I have got is the scrolling background is hidding the birds, planes and clouds objects which scroll up, this problem is driving me mad, can any of the more experienced programmers help before i go completelly mad trying to solve this annoying problem.
package
    import flash.display.MovieClip;
                import flash.text.*;
                import flash.events.Event;
                import flash.events.KeyboardEvent;
                import flash.ui.Keyboard;
                import flash.display.Stage; 
                import flash.utils.Timer; 
                import flash.events.TimerEvent;
                import flash.utils.getDefinitionByName;
    public class game_code extends MovieClip {
         public  var sky_Diver:sky_diver;
         public var leftArrow:Boolean = false;
         public var rightArrow:Boolean = false;
         public var BackGround:clouds;
         public var BackGround2:clouds;
         public var BackGroundBreadth:Number;
         public var BackGroundContainer:MovieClip;
                     public var scrollSpeed:uint = 1;
                                 var score:int = 0;
                                 public var nextObject:Timer;
                                 public var objects:Array = new Array();
                                 const speed: Number = 9.0;
        public function game_code(){
            sky_Diver = new sky_diver();
                                                BackGround = new clouds();
                                                  BackGround2 = new clouds();
                                                sky_Diver.x = 200;
                                                sky_Diver.y = 200;
                                                BackGround.y = BackGround.height;
                                                 BackGround2.y = 0;
                                                 BackGround.x = 400;
                                                BackGround2.x = 400;
                                                BackGround.scaleY = 1;
                                                BackGround2.scaleY = 1;
                                                BackGroundContainer = new MovieClip();
                                                 BackGroundContainer.addChild( BackGround );
                                                 BackGroundContainer.addChild( BackGround2 );
                                               stage.addChild(BackGroundContainer);
                                                stage.addChild(BackGround);
                                                stage.addChild(sky_Diver);
                                               setNextObject();
                                                stage.addEventListener(KeyboardEvent.KEY_DOWN, keyPressedDown);
                                                stage.addEventListener(KeyboardEvent.KEY_UP, keyPressedUp);
                                                stage.addEventListener(Event.ENTER_FRAME, movesky_Diver);
                                                stage.addEventListener(Event.ENTER_FRAME, moveScroll );
                                                stage.addEventListener(Event.ENTER_FRAME, moveObjects);
                                                                // set arrow variables to true
                                 private function keyPressedDown(event:KeyboardEvent) {
                                                if (event.keyCode == 37) {
                                                                leftArrow = true;
                                                } else if (event.keyCode == 39) {
                                                                rightArrow = true;
                                // set arrow variables to false
                                private function keyPressedUp(event:KeyboardEvent) {
                                                if (event.keyCode == 37) {
                                                                leftArrow = false;
                                                } else if (event.keyCode == 39) {
                                                                rightArrow = false;
                                // move every frame
                                private function movesky_Diver(event:Event) {
                                                var speed:Number = 15;
                                                if (leftArrow) {
                                                                sky_Diver.x -= speed;
                                                if (rightArrow) {
                                                                sky_Diver.x += speed;
                        public function moveScroll(e:Event):void{
                                                BackGround.y -= scrollSpeed;
                                                BackGround2.y -= scrollSpeed;
                                                 if ( BackGround.y < -BackGround.height){
                                                  BackGround.y = BackGround.height;
                                                else if (BackGround2.y < -BackGround2.height){
                                                                BackGround2.y = BackGround2.height;
                                                public function setNextObject() {
                                                nextObject = new Timer(500+Math.random()*1000,1);
                                                nextObject.addEventListener(TimerEvent.TIMER_COMPLETE,newObject);
                                                nextObject.start();
                                public function newObject(e:Event) {
                                                var goodObjects:Array = ["cloud"];
                                                var badObjects:Array = ["plane", "bird"];
                                                if (Math.random() < .5) {
                                                                var r:int = Math.floor(Math.random()*goodObjects.length);
                                                                var classRef:Class = getDefinitionByName(goodObjects[r]) as Class;
                                                                var newObject:MovieClip = new classRef();
                                                                newObject.typestr = "good";
                                                } else {
                                                                r = Math.floor(Math.random()*badObjects.length);
                                                                classRef = getDefinitionByName(badObjects[r]) as Class;
                                                                newObject = new classRef();
                                                                newObject.typestr = "bad";
                                                newObject.x = Math.random()*500;
                                                newObject.y = stage.stageHeight;
                                                addChild(newObject);
                                                objects.push(newObject);
                                                setNextObject();
                                public function moveObjects(e:Event) {
                                                for(var i:int=objects.length-1;i>=0;i--) {
                                                                objects[i].y -= speed;
                                                                if (objects[i].y < 0) {
                                                                removeChild(objects[i]);
                                                                objects.splice(i,1);
                                                                if (objects[i].hitTestObject(sky_Diver)) {
                                                                                if (objects[i].typestr == "good") {
                                                                                                 score += 1;
                                                                                } else {
                                                                                                 score -= 1;
                                                                                if (score < 0) score = 0;
                                                                                scoreDisplay.text = "Score: "+score;
                                                                                removeChild(objects[i]);
                                                                                objects.splice(i,1);

Answer 1

Chipleh is probably right as far as the order in which you add things.  Another thing you might not realize is that within a few lines of code you reparent the background...
BackGroundContainer = new MovieClip(); 
BackGroundContainer.addChild( BackGround ); // first you add it to the container
BackGroundContainer.addChild( BackGround2 );
stage.addChild(BackGroundContainer);
stage.addChild(BackGround); // then you relocate it onto the stage