Explanation:

Statement 1 is correct. The main valley is eroded much more rapidly than tributary valley because it contains a much larger glacier than tributary valley.
Statement 2 is incorrect. The main valley contains larger glaciers than tributary valleys.
Statement 3 is correct. Hanging valleys forms a natural site for hydro power generation due to the presence of waterfalls.

Hanging valleys are shallow canyons formed over a larger canyon, and are tributary valleys to the larger valleys. The hanging valleys are so named due to their positioning of being above main valleys. Hanging valleys form a characteristic U-shape above their respective main valleys, and have a steep wall at the point where the two valleys meet. These valleys are found in regions of high altitude, particularly in mountainous regions. The valleys are natural crevices through which rivers flow, and at the cliff meeting point where the two valleys meet the rivers dramatically drop to form waterfalls. In most cases, the hanging valleys are smaller than the main valleys. However, some hanging valleys are also found underwater in fjord systems where hanging fjords are shallower than the main fjords.
Hanging valleys are formed as a result of the erosion effects of glaciation. The valleys are thought to have been formed by two different glacier flows that interact with each other. A glacier with the relatively small amount of material flows into the main glacier with the more glacial material. The main glacier with huge volumes of glacier material ultimately erodes away either through abrasion or plucking, with vertical erosion forming extremely steep valleys with vertical slopes, while lateral erosion is widening the valley walls. The hanging valleys formed in this way have U-shaped walls.