Now powerline lights on all powerline devices are on? The smaller one in WPA2220KIT is conencted to the main router? Run the MAC utility and login web interface to find out the current password. If...

You have to be a little patient. If it is verified as the same problem before with W9980, they should be able to provide a quick solution to it. :)

No such a feature.

There is no compatibility list or update list for Win 10 from TP-LINK as a reference...I won't give you any advice... Let's wait for some time if it is not quite urgent...

We can login its web interface to go to Quick Setup to configure it. http://www.tp-link.com/en/faq-87.html

If hardware version of your WR841N is V8, you can only upgrade firmwares for V8. We cannot upgrade firmwares for V10. http://www.tp-link.com/en/download/TL-WR841N_V8.html#Firmware