Thank you for the report, that is a bug in Alpha 6. It will be fixed in a future version.
That is not a bug. Extender settings that are configured by the controller are locked in the extender web UI.
However, at the moment some Wi-Fi parameters are still configurable only via the extender web UI, you can see them if you click on the “Advanced Settings” link in your screenshot.
Basic Wi-Fi settings on the extender (SSID / Network protection / Password / ...) in both bands are synchronized with the controller. This is part of the Mesh Wi-Fi system design.