i am a bit confused. If you have used the HG635v1.04t_multicast_with_multicfg_main.bin file to do a firmware update you will have telnet access after doing a factory reset, you don't need another config file but you will need to set the router up. The telnet access will be open on the WAN as well as the LAN. It is best to make all the setting changes that you want and then set the remote management port, which defaults to port 23 in that firmware, to another value e.g 7547 is TalkTalk value. Use shields up to be sure that things are secure.