The wrinkling happens because the thicker skin on our hands and feet soaks up water. Notice that the thinner skin on most of the rest of your body doesn't get wrinkled, only the callused parts. Ultraviolet light from the sun changes a form of cholesterol in your skin to vitamin D. Only about 15 minutes a day in the sunlight is necessary. You can also get vitamin D from fortified dairy products, and in lesser amounts from tuna, salmon, and fortified breakfast cereals. Humans need oxygen to breathe.
Blood is normally a bluish color, but turns red when oxygen is present.
In space, there isn't any air, which means you blood should be blue if you get cut. The sun can give people energy in a couple ways. When sunshine warms your body it is giving you some heat energy through radiation. The most important way the sun gives us energy is through the food we eat. Plants can convert the suns energy into food for itself, which we can eat.