Frankly speaking, the arrange is really rushed. The Forbidden City is closed at 16:30 and needs at least two hours for a brief visiting. It means that you have to enter into the palace at least before 14:30. Seems impossible.As for the Tiananmen Square, it is opened 24 hours but the other attractions in the square may be closed after 17:00. So, you could only have a walk in the square~