Ueda and Ellen have given good answers. "Venom" is a type of poison that is injected by an animal when it bites or stings you. Bees have venom. Some snakes and spiders have venom. "Poison" is something that can cause (chemical) harm if you if you eat or drink it, breathe it, absorb it through your skin by touching it, OR get injected with it. For example, some frogs have poison on their skin. Many cleaning products are poisonous. Chocolate is poisonous to dogs, but not to most humans.

Yes. Something is poisonous because if you eat it, you will die (eg poisonous mushrooms). Something is venomous because if they bite you, you will die (eg venomous snakes).

I heard "poison" means something that causes death or harm when swallowed or absorbed in a living creature. On the other hand, "venom" means a specific kind of poison that is produced only by snakes, spiders, bees, and so on. The latter can do harm only when such creatures bite or sting others.