2: implicit world. Reacts to but not modeled.
3: explicit world and your separation from it.
4: Model that includes other intelligences of level 3 that you have to take into consideration. World resources can be shared or competes for.
5: Language. Model of others as yourself, their model include yours too. Mutual recursion. Information can be transmitted mind-to mind.
Next, we gotta ask ourselves, could you have substrate independence? A thing that isn't biological, but can model other level-5 creatures?
My guess is yes. There's all sort of other substrate independence.