You should enable port forwarding. And I think it can be found in User_Guide

In general, MIMO PLC use L*N, L*E.

TPL-406e? I cannot find this model. But I think you can try plug them in the same room to avoid the interference in the circuit to test.

Did you follow the FAQ to setup? Make sure the Location and Time of the app is set correctly. http://uk.tp-link.com/faq-947.html

Yes, you can control them remotely, just make sure the Remote Control is enabled on the smart plugs. You can turn off the wifi on your phone, and turn on 4G, and see if you can control them.

You can turn it off and on manually, but cannot do (power off, count 10 seconds, power on).