case 1, sure for Windows machines you can use AnyConnect 4.1 with the ISE Posture module.
case 2, not possible, anyconnect posture only works on desktop o/s's
case 3, you can set the default posture as "compliant" for devices that can't do posture, so then they will just be "compliant" and match the rules that require "posture_status" to be "compliant"
Base licens, does not enable posture, this is part of APEX (use to be called advanced)