No, one more time, The router has two sockets, one your phone line goes in and one your Ethernet cable goes in if you are on a Lan and not wifi, You must disconnect the phone line to enable the FW to...

Sounds like either a bad cable as Kev said or the port is worn out and not comm'ing with the cable anymore, I would also try a factory reset myself incase some of the ISP settings have corrupted...

Yeah it means any client on your network will not be able to communicate with another client on the same network I'm afraid, you may have a setting for rules though that may enable you to place the...

What I mean is whether you are Ethernet or wifi connected isolate the router from the internet before attempting any flashing of the router or it will chuck you an error code, wired is best due to...

Make sure you have the router connected to the PC and then disconnect the line from the phone socket, hth.

The answer is probably that you are at risk if all the conditions are right for whoever is scanning you if at all, most router security issues right now relate to risks to those connected to you...