Fibre Pre-Installation Question & Issue

[#1]

Fibre Pre-Installation Question & Issue

Question
When the BT / OR engineer comes to do the installation and fitting an extension, what is it they are extending ?
a) is it the main BT master socket that is extended so you can place the modem in a place of choice rather than next to the current master socket ?
or
b) an extension of the data cable between the modem and router so the modem can stay near the current BT master socket and the router can be placed near a different electrical mains socket in a place of choice ?

Issues
I have just received the new router in preparation of my fibre upgrade next week but have noticed a couple of issues before i have even begin to use it.
a) The router is not designed to work in a fibre enviroment. It has been modified with its firmware to be made to work with it with redirecting one of the LAN ports ruling out the use of that port.
b) Since one of the LAN ports is now disabled 4 connections (TV, computers and games consoles) into 3 don't go this and gives me a problem i don't want and is not ideal.
Before anyone mentions just use a switch i already have an over crowded number of devices and power supplies and i am already adding an additional unit in having seperate modem and router to start with and don't want a 3rd unit to replace just the 1 currently in use.
I can find no official user/setup manual that mentions that this router is suitable or compatible to be used in a fibre setup so can only assume it is modified.

[#2]

Yes, the TG582n will work on fibre as its an ADSL router running modified firmware to use one lan port for the openreach modem link, as you assumed it was.
As for the extension kit, I requested one but it wasn't offered or mentioned by the engineer and the same thing happened to another user on here.  So I cannot tell you what it is correctly.

[#3]

The extension is a data only extension from the master socket to the place where the BT modem sits. you must then connect the plusnet provided router from the ethernet socket marked in red to the ethernet socket on the router. You can also buy a router such as the Netgear WNR2200 which does have the facility to connect on an ethernet socket as its primary connection leaving its other 4 ethernet sockets available, I tried this and found the wnr2200 to be not as good or as quick as the TG582 that plusnet provided so my wnr2200 is back on ebay now. There is also a Draytek modem router that can be used to replace both the BT modem and the plusnet router, but at £170 or so for one I think it is a bit too high a price to pay, especially as with all the setups that are different from what is provided there will be no support available.