I can tell you only what I would use these 2 words in. If it is a large area, than it is a region. Example: I live in the Northwest region of the United States. An area I would usually use it for smaller places. Example: This area of this room is used for books. I would never say This region of this room is used for books. So for myself, I use area for smaller places and for larger places I use region. I hope this helps.

I can answer the tomorrow part: mañana is tomorrow. It sounds like Men-Yanna in english.

Everyone has certain degrees of digesting milk. If you drink a gallon of milk within 30 minutes, your body will not digest it and you will get sick. Certain people get sick with a glass milk.

Yes they are similar, but as explained, when you use a froth is when you are are talking about the top of a beer when poured. Fire departments put out some fires with foam. In that case, foam is a chemical.