yes you can get an output through LAN port on the tplink router

I've confirmed with tplink support, the new firmware 20161018 uses new VI, means the web UI would be a bit different, but it's OK to upgrade it. and a reminder, don't upgrade with any USB devices...

the td-w8968 can be used as a 3G router by inserting a usb dongle in it, or you can use the 3G dongle as a backup for internet access. but if you mean really boost the 4G signal, that's not gonna...

disable the DHCP of both extenders, let the router be the only DHCP server. and you can check the firmware version of the extender, update if it's not the latest.

SSID can be the same as that of router's. what kind of conflict you experience? when you set up the extender, I think it's better to set up one at a time, then unplug it and configure the other one.

was the RE led still lit? do you have the same issue with your home network? maybe unplug the extender for a while to test. or if you have created a separate network name for the extender, then you...