The KeyboardEvent instance contains data about the event itself, part of it being keyCode, which gives the code of the pressed key. Using this property, you can detect which key the user pressed, and react accordingly.
As you understood, you can use gotoAndPlay() and gotoAndStop() to move around your animation.
It gives us the following code :
stop();
stage.addEventListener(KeyboardEvent.KEY_DOWN, fl_KeyboardDownHandler);
function fl_KeyboardDownHandler(event:KeyboardEvent):void {
if(event.keyCode == Keyboard.Q) {
gotoAndPlay(1); // Back to the start
} else if (event.keyCode == Keyboard.W) {
gotoAndPlay(currentFrame-1); // Back one frame
} else if (event.keyCode == Keyboard.E) {
gotoAndPlay(currentFrame-1); // Forward one frame
} else if (event.keyCode == Keyboard.R) {
gotoAndPlay(100); // Go to 100th frame
}
}
Note that I am using the Keyboard class to get the keyCode associated to a specific key.