No you can't.
Wrong. You absolutely can use pre-generated keys for google's authentication services. They call them backup codes.
Authenticator runs on a phone or tablet. Without internet you can't even set it up.
Wrong again. You can absolutely setup accounts in Google Authenticator (And most other similar apps) without network access. You can even install the app itself without access in many cases, if you want to side-load from a PC or something.
Without perfect clock sync the codes generated by authenticator stop working.
Sorta wrong. The clocks don't have to be perfect, they just have to be close. Pretty much every service has the ability to deal with a certain amount of clock skew. Smartphones these days are pretty good at keeping time, even when not connected to the network, so this usually isn't an issue. But this is also dependent on if the service is using TOTP or HOTP. (Time based or Counter based codes)
The codes generated by authenticator have a very short shelf life, measured in seconds.
Here you got one right, every code has a 60 second lifespan. (:
But to the point of the original post (GGGP?) that brought up the autheticator... They should at least have HOTP/TOTP as an option for those with smartphones in this case. They probably can't drop SMS altogether because of the users that *don't* have smart phones, but no reason not to support both.