How do I set up a daily schedule for a zone that waters at 7am and 7 pm daily?
The only way to currently do that is setup two schedules with two start times. The great thing about that is they will each be able to take advantage of our weather intelligence features at different times per/day.
Is there a way to schedule a interval watering of every 12 hours?
Not currently. Hourly supports up to every 6 hours.
So, I live in the desert southwest–hot dry. I could water my hanging plants say 2 minutes every six hours?
Yes, our hourly schedule allows for that.