You can add "Timeline Actions" to stop a timeline. So, at the 3 second location, there would be a timeline action that pauses the timeline. The problem is that timeline action might stop the action when the timeline is played in reverse... from 3 to 2.
To prevent that, you could start the reverse at just below 3 seconds or you can add a JavaScript to the Timeline Action. Detect the direction the timeline is going. If forward and the timeline is >= 3, then pause. Otherwise, play in reverse. Variables might he helpful to keep this straight.