For 3. Two living parts could be the grass and one of the other animals, while two non living parts would be Oxygen and the sun. Oxygen interacts with the animals and provides life, while the sun provides growth to the grass, and the grass provides food for the consumers. And a consumer like the snake, provides the continuous chain and food for the next consumer
4. The ultimate of energy is the Sun. It provides energy to the grass, which then starts the food chain. Without the sun food chain simply wouldn’t work, and it would die off quickly.