Anyone knows what is the role of “里” in this case？
哪 + 里 = "Where.“ There are also some lessons that use "哪儿" as meaning "where." It's the same thing, just a Beijing dialect.
Is 哪里 or 那儿 the Beijing dialect?
哪儿，那儿 and 这儿 are all Beijing dialect
How would I ask for directions to an outdoor or street market?
菜市場 is wet market but it literally means vegetable market. 跳蚤市場 is flea market or street market.
超 (chāo) = to exceed/super-/ultra-
市 (shì) = market/city
超市 (chāoshì) = supermarket
duolingo said it wrong