We had to remove the old app at Nest's request, because it didn't meet their guidelines.
It's the same thing with the home/away device in a scene: Nest requires that the user is prompted when changing the Home/Away mode. Doing that in a scene is automated and the user can't be prompted, therefore we had to remove that option.
The one temp setting for Auto mode is a limitation of our UI. Currently, changing the setpoint while in Auto mode will set the lower temperature (the heat setpoint) to the shown setpoint -2, and the higher temperature (the cool setpoint) to the shown setpoint +2.