Hi! I've been working in DWH some years, in my expierence i could say about question 1&2: a data warehouse is not only for querying data, it allows you to get information(next level of data) and explode them with anothers tools like PowerBI, Microstrategy, etc. I didn't know about an app the reads a data warehouse.
Datawarehouses get updated in batch, it's not common a streamming updating, this is an app database behaviour.
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