Do you mean connect a switch in PLC? Yes, the PLC can be regard as a cable, if you are sure that it is not forming a loop a loop.

In different phase, the link of PLC devices may be influenced, so please use them in the same phase. This link may help you. http://www.tp-link.com/en/faq-406.html

1. WiFi Clone will copy the SSID and password of your router. If the strength of the wireless signal from extender is better than the router, it will switch to connect the extender automatically. 2....

If it's a USB printer, printer controller is needed http://www.tp-link.com/en/faq-640.html

you can set PPTP VPN, OpenVPN and IPSec VPN on the router. http://www.tp-link.com/en/faq-1751.html

Confirm with ISP whether VLAN tag is required on the router. If yes, you should be able to use D5