How about status of powerline light on all powerline devices? You may have to pair them first. http://www.tp-link.com/en/faq-258.html To change wireless settings of WPA4220, refer to the guide below....

Refer to the guide here. http://www.tp-link.com/en/faq-434.html

No... their Mi-Fi devices have no ethernet ports for wired connection.

Good share! To contact ISP and get correct configuration details is the first and most important step there...lol...

There are many differences...including chipset, appearence, features etc... V3 should be better as more features are added and it has a better performance as well... most importantly, it is NEW...

What's the firmware version of your W9980? How many devices are connection when it crashes? ADSL light and internet light are normal all the time? Did you try to contact TP-LINK support team?...