<image>A stunt flying team was performing in a famous scenic area - the Tianmen Cave in Zhangjiajie. The altitude changes of one of the planes after takeoff are shown in the table below:  (1) How many kilometers higher is this plane compared to the takeoff point at this time? (2) If the plane consumes 2 liters of fuel for every 1 km of ascent or descent, how many liters of fuel did this plane consume during these four maneuvers? (3) If there are 4 required maneuvers during the stunt performance and the altitude changes for the first 3 maneuvers after takeoff are as follows: ascended 3.8 km, descended 2.9 km, and then ascended 1.6 km, if the plane is to be 1 km higher than the takeoff point at the end, should the 4th maneuver be an ascent or descent, and by how many kilometers?