AFTV2 - Custom DNS Server setting does not work on WiFi connection

I have noticed on the AFTV2 that custom DNS setting only works on the WIRED network. If you try the same on the WiFI connection (by clicking Advanced in the popup window) ... it will pretend to accept the custom DNS ... but instead rolls back to the DNS supplied by the DHCP server.

I need the custom DNS to work on the WiFI connection. My Apple TV box also has a custom DNS - so Amazon need to fix the bug .. without me having to root the device etc.

Any Sideloaded Apps for AFTV2 that play in 3840x2160 mode?

I have the FireTV 2 and the only two apps that switch the screen to 4K are Netflix and Amazon. The Youtube app plays everthing in 1080p even if its a 4K video. This means that the Netflix and Amazon apps are sending some command to the Fire TV OS to switch from 1080p to 2160p.

Can someone explain that - also are there any side loaded apps that will display 4K videos or 4K photos in 4K ?