What's the hardware version and firmware version of your W8968? Is the firmware up to date? Provide the topology pls.

When DHCP is not working, you should not be able to login its web interface. If so, how did you check the system log? To restart the router instead of hard reset it cannot make it work? Try to...

On your PC, can you ping 192.168.0.2 successfully? Check anti-virus software and firewall settings.

You can access web interface of WPA4220 by its utility. http://www.tp-link.com/en/download/TL-WPA4220_V1.html#Utility

It seems that you have much misunderstanding... No 3G/3.75G/4G router can support all modems... no such powerful devices yet... MR3420 V2 supports 4G but it also can work with 3G/3.75G modems.

Herbert, NC200 is not an IP camera but a cloud camera. As I said, you can follow the instruction to access it remotely. We cannot access it remotely via VLC.