Android Auto questions

My new car will support Android Auto, but my dealer is clueless about it (and so am I), so I need to ask here.

Here my questions.
1. I use HERE WeGO and never Google Maps. Reason be is that I can download maps of a whole country for it. I am on the road a lot in black holes (no network) so this is a must. Plus, I like the App. Would it work with Android Auto?
2. If HERE WeGO does not work with Android Auto is there a navigation app where one can download whole countries and use it with Android Auto?
3. Can one use Android Auto without a data plan? I suspect it be limited in its functions but that is fine.
4. Any other tips?

Thanks James.

So are you saying it does not work online at all? Regardless of what navigation application I use?

PS
Wave does not allow the saving of maps and can only do of-line if you saved a specific route beforehand.
Not ideal.