(1): By default you hear dialtone on your phone. With a setting change, you can configure to have a distinctive dialtone indicating no service. If you dial a number you hear a voice speak 'No service is available to complete your call.'
(1)(a) Yes, calls are forwarded and GV will see the Obi as any forwarding number that is out of service.
(1)(a) No.
(2):
- Via the ObiTalk Portal, when an internet connection is made available the Obi connects to the ObiTalk servers, retrieves it's configuration, and boots up. Total time about 45 seconds, IME.
- Via the the Web Server-Based Local Configuration (also called The OBi Device Management Web Page also called direct IP address interface), which I doubt you're doing because you're a new user, it works like most other modern electronics with non-volatile, even when powered off it retains settings and configuration. I don't know the upper limit for time off is, I'm certain a week is well below the upper limit though.
(3) Yes. See this for a lot of details:
http://voip.mi-telecom.org/See this for a shorter summary:
http://www.wire-your-phones.com/