Questions About The RTS Part of The Game

I usually ask my questions in the Q/A thread and suggest others to do so. However I have a couple questions this time so didnt want to flood there.

1)What happens when I retreat my ATs in the middle of a battle?

2)What happens if morale gets very low?

3)How does the game decide whose ATs will be used first in a match with 10.000 infantry?

4)Why is upgrading ATs super cheap with gold compared to warfunds?

5. I really need a couple of ATs but I only have one. Should I invest in a 12 or 15 level infantry?

6. How is the HnG app? I didnt hear good things about it but I would like to hear it in detail from someone who tried it.

EDIT: Forgot one. Best way to gain warfunds?