Although a master socket is shown in image 2 , it has no master socket function, ( in other words the extension sockets are all wired from the same place ( assuming they are not connected from the master socket consumer panel but the A/B wiring connections ) , so chances are the extensions would continue to work when the master socket is disassembled ( when wired correctly that should disconnect them ) and any defect present on any of the sockets or wiring affects the ‘line’
In image 1, yes you could connect a router into the socket at the end of the daisy chain, but the broadband performance may suffer, if the extension wiring is of poor quality, or the ‘bell wire’ is connected in the daisy chain....2 wires are all that need to be connected , but quite often a third wire is connected ( useful when rotary dial phones were in use ) but unnecessary with modern phones and can have a negative impact on broadband performance.
If connected correctly ( as per image 1 ) and you have concerns about your service, your ISP would ask you to connect in the master socket test port , doing this eliminates ( disconnects) all the extension wiring and extension sockets , so if a defect is detected it ‘must’ be on what Openreach are responsible for , if not as per image 1 , then connecting in the test port doesn’t prove anything as the extensions continue to be connected to the line.
