Apple refurbished

Yes, Apple has an online refurbished store in Australia -> Certified Refurbished Products - Apple (AU)

The only source of Apple OEM refurbished devices is from Apple itself in those countries where they have an online refurbished store.

If the device is refurbished by Apple, unlocked and SIM free, then you sare okay, but it depends on what country you're going to use it.

See LTE compatibilities here:--> iPhone - View countries with supported LTE networks - Apple

Regards

Giulio

No, at the moment only iPads and Macs, see here: Certified Refurbished Products - Apple (AU)