It's harder to block sound because sound waves and transverse waves, causing the sound to bounce off objects. This isn't the same with light.
I think the hydra lacks the specialized cells for touch and chemical detection. On the other hand earthworms have touch, light, vibration and chemical receptors along the entire body surface. Both of them are invertebrates (those animals without a backbone), they include insects, worms, jelly fish, spiders among other animals.
No. Not all organisms. Because in a way fish are organisms and there are some that live way down in the deep dark water. And they cannot swim up to where the sun is or they would disintegrate. So the answer would be no, not all organisms depend on the sun for energy. Different organisms have different ways of getting energy.
Do you have any multiple questions?
