Event.ADDED_TO_STAGE is running twice...

You can do something like this :

package

{

    import flash.events.Event;

    import flash.display.*

    public class Testing extends MovieClip

    {

        public function Testing()

        {

           if (stage) startapp();

          else addEventListener(Event.ADDED_TO_STAGE,startapp);

        }  

        private function startapp(event:Event = null):void

        {

            removeEventListener(Event.ADDED_TO_STAGE,startapp);

            trace('start app')

            //instructionscreen()

            closebtn.visible=false

            closebtn.alpha=0  

            //controls.alpha=0

        }

    }

}

Also remove the Event.ADDED_TO_STAGE listener in startapp function.

package

{

    import flash.events.*;

    import flash.display.*

    public class Testing extends MovieClip

    {

        public function Testing()

        {

            addEventListener(Event.ADDED_TO_STAGE,startapp)

        }   

        private function startapp(event:Event):void

        {

            trace('start app')

            //instructionscreen()

            closebtn.visible=false

            closebtn.alpha=0   

            //controls.alpha=0

        }

    }

}

its running for once only