The authorization is usually for PPPOE. But Singtel does not do that (Some one told me M1 needs PPPOE). For Singtel just a DHCP client is enough to work. The authorization is done by something like a customer ID is stored in HW8244H. When HW 8244H connects to the upper device the ID is validated. ( After I move to another BLOCK, HW 8244H failed to connect to upper device. The guy from Singtel update this ID to make it work again).
For multi dial-up, I have not tried it yet. But I believe Singtel should not be that stupid to allow multi dial up (Or you can, but your total bandwidth remains unchanged).