As we always say eat food and rest because tomorrow you have to go to work. When we throw a ball up, it gains a max PE at some height. More the height more energy it has which makes it do more work. Is this right to say?
Yes, the higher the level of water in a dam, the more work the flow of water can do onto the blades of the water turbines-generators, which can produce more electrical energy.
Previously, the Sun energy via evaporation increased the potential energy of the water of rivers, lakes and sea up to the clouds level.
Then, rain replenished the water level in our dam.
Not exactly. The ball has all of the energy that it's going to have when you release it. Some is Kinetic (velocity) and some is potential (height). When it stops at max height, the potential energy is maximized but the total energy is unchanged.