This guide will show you the prerequisites for your unlocked Fire TV device including (4K Mantis), (HD Tank), etc. It's always important to know not to backup both the vendor and vendor image in TWRP because I was affected by it on two Fire TV's that don't have factory images unlike the main android phone in which has factory images (LG, Samsung, etc.) Ok the main point here is to warn you guys to NOT backup the vendor and vendor images since they make the Fire TV device brick and unbootable regardless what prerooted rom you flash, what you wipe in recovery, factory resetting the whole device WILL NOT fix this problem. Always backup system, boot, data only and you should be fine. Although there's an issue with the restoration process as well rebooting me to TWRP after a successful backup restoration, there's a simple fix for that. Flash a prerooted rom and you're good to go! If somebody in the XDA community for Fire TV devices reach out to me on showing us how to flash the vendor.img and other important files in fastboot mode with a working iso that can support fastboot functionality for Fire TV when you get into these issues. If you do end up backing up both vendors and restoring it as a TWRP backup, it wipes system components of your device which make your device stay on the Amazon screen (HD Tank) firetv (4K Mantis). Please take note with this issue so you aren't affected by this and ask questions if needed. We also need a more stable TWRP recovery image for Fire TV Stick 4K without vendor, vendor image, system image in the backup when backing up your device and other important bugs that need fixing (APPLIES on all recent Fire TV recoveries) They're very unstable and cause a ton of problems which cannot be currently resolved in this moment in time.