Originally Posted by cxl000
You may not need an unlocker.
As a simple test unpack recovery, modify icon_error.png, repack, dd to recovery partition and reboot recovery.
I'd be interested to know if this works on releases other than 220.127.116.11
It's a little more complicated than that because you can't modify the contents of recovery because the stock bootloader does a signature check. But I have a fully working solution for loading recovery, I'm just waiting on the last and final pieces. As long as you have root, it will work.
Originally Posted by superkoal
If you can boot AOSP - can you also boot an older (rootable) firetv firmware if your device is shipped with a new build?
Booting AOSP requires certain things that can only be done if you have root. The only way currently to downgrade is to stick a file in /cache/recovery and boot into the recovery. Writing to /cache requires having root.