Something is hollow if is hard, but there is nothing inside. When you knock on something hollow it makes a different noise to knocking on something solid. Trees often become hollow if termites eat the center of them away.
Something is homemade if has been made at home from all the individual ingredients, rather than from a store-bought mix. Food made in a large quantity in a commercial manner is not homemade. Homemade usually refers to food, while handmade refers to other items.
You feel hot when the temperature gets high. It is hot in summer. Fire is hot, and food or drink that is freshly cooked is hot. It is very painful to touch something that is very hot, and it can leave you with a nasty burn. The picture is of some hamburger patties being cooked on a hot grill.