Questions about stacked combat

[WesW]

I am considering adding stacks to my mod, and I have a few questions.
Does the AI recognise that it can make stacks and use this feature?
When defending, how are units chosen for combat, and is the entire stack destroyed if a defender is destroyed?
Thank you for your help.

 

[Ddude97]

The rules and such for stacks are going to be governed on how you make them, considering that the game doesn't really some with them...