Good day @Alicetang,
Welcome to TPG Community!
For the NBN FTTP technology, if the NTD (Network Terminating Device) Box is not yet installed in the premises, an NBN technician will be sent to install it, which requires for you to be on the premises since they'll be providing you the options on where to have it.
If the option given includes your living room, then it will be installed there.
The NTD and NBN box is just the same, unless you are talking about the router as your NBN box?
Once the NTD box is installed, the NBN router needs to be connected to the designated port of it for you to be able to receive the internet service. The NBN router that we are providing our customers comes with an Ethernet cable (around 3 metres) which you need to use to connect it to the NTD box.
With the said cable, eventually the NBN router will need to be close to your NTD box.
You do have an option to purchase a longer Ethernet cable for you to place the NBN router to any location of your house as long as the other end is connected to the NTD box.
If you need to relocate the NTD box, you need to contact NBN Co directly to request for it to be moved, however, fees may apply.
The basic exclusions are more than 30m from the lead in, wet areas such as bathrooms, kitchens, laundry, pool areas, poorly ventilated cupboards, ceiling or wall cavity and needs to be near a dedicated power source.