The firmware is right. You can try to upgrade the second firmware first.

Did you setup a static ip address on the server? The clients with a static IP address will not show up in the DHCP client list, cause the IP address is not assigned normally by DHCP.

It seems the repeater ping NTP server to test internet connection. it is not a problem and It won't cause internet issue normally. Perhaps you can send a feedback to TP-Link and see if they can...

Deco doesn't support VPN and can't be a VPN server. It only supports VPN passthrough.

I replied your previous post. The switches are just not configured fine. Using Kasa to add them first and enable remote control, they will work.

Smart plug can't provide internet, so it is normal when you see "internet not available". Following the steps below, it should be working: http://www.tp-link.com/us/faq-1247.html