[Kindle Fire HDX 7" & 8.9" General] travanx:
I started downloading and installing everything, and while doing that the Kindle won't let me save the edited build.prop using es file explorer or build prop editor. I can't seem to change permissions of the file either. Bummer. Should be interesting upgrading to 13.3.2.6 to rollback. Hoping to not brick the device, but its on its last legs anyways.

This is where my downgrade didn't go as smoothly as planned.

Got this from the command prompt.

Adb shell chmod 644 /system/build.prop

Unable to chmod /system/build.prop: Read-only file system

OTA?

Go into wireless and forget your wireless settings passwords. If the Kindle can't connect to wireless how is it going to download an update? I guess turn wireless off to be extra cautious. Disabling and renabling OTA updates through KDFX seems to mess up the check device thing to update the internal sd card bin files for the steps below.

Remove Safestrap

Boot into stock rom slot.

Go into safestrap and uninstall recovery.

After this I reran KDFX to towelroot and put su on, just in case.

Update to 13.2.2.5 for the Eventual Downgrade tp 13.3.1.0

http://xdaforums.com/kindle-fire-hdx/general/update-1314-4-1-1-probably-sangria-t2901813

Had to factory reset, before the device would even see any bin file. Ended up using the 13.3.2.5 bin file. Would not update to 13.3.2.6. The device would say its not valid and delete the file. You weren't kidding that this is not straightforward.

https://s3.amazonaws.com/kindle-fire-updates/update-kindle-13.3.2.5_user_325001120.bin

Downgrade to 13.3.1.0

After I got 13.3.2.5 on the device I used the install.bat from here

http://xdaforums.com/showthread.php?t=2782159

The final step of following the instructions of putting 13.3.1.0 on internal card and rebooting did not work. I had to yet again factory reset, then put update-kindle-1X.3.1.0_user_310079820.bin back onto the internal sdcard. And then finally got to 13.3.1.0.

No matter what I did to upgrade and downgrade these bin files they wouldn't take unless I factory reset each time.

Install TWRP here

Make sure you have root through towelroot and su, using KFHDX+ToolKit+v0.95 .

http://xdaforums.com/kindle-fire-hdx/development/recovery-twrp-recovery-2-8-1-0-apollo-t2991155

TWRP Flashable .3.2.3 Bootloader Upgrade here

http://xdaforums.com/kindle-fire-hdx/development/twrp-flashable-3-2-3-bootloader-upgrade-t3025504

Create Unlock File

Once that was done I went through the steps for the unlock file here

http://xdaforums.com/showpost.php?p=58897784&postcount=67

Fastboot on windows 8.1 x64 is something special.

With the device plugged in, uninstall the adb driver from device manager and reboot.

This video helps explain how to install the fastboot drivers, sort of, https://www.youtube.com/watch?v=afrvSGiMAtk. Or follow text below.

Mouse over to top right of windows screen for the charms menu.

Click settings at the bottom.

Change PC Settings

Update & Recover

Recovery

Advanced Startup

Restart Now

At this menu click troubleshoot

Advanced options

Startup Settings

Restart

Then type 7 to force driver install without signatures.

Fastboot Into the Kindle

From there boot the Kindle into fastboot. I held down power/up volume/down volume like another thread suggests. Or go into TWRP->Reboot->Bootloader

Download this driver and put the unzipped folder somewhere.

http://xdaforums.com/showpost.php?p=59268023&postcount=8

When TWRP says fastboot, plug the USB cord from the motherboard port (not external ports) to the Kindle. In device manager fastboot hopefully shows up and forces the install of the downloaded drivers. I had to uninstall whatever yellow triangle drivers were showing up, until fastboot would finally show. It will give a red box saying are you sure. yes I am sure, and now you have working fastboot drivers on Win 8.1 x64.

Install Minimal ADB and Fastboot

At this point, I was sick and tired of going to the Android Studio directory and used minimal ADB and Fastboot instead.

http://xdaforums.com/showthread.php?t=2317790

Finally unlock the bootloader

Copy the unlocked file into wherever your fastboot.exe is located. And type below line by line.

fastboot -i 0x1949 devices

(Makes sure a device shows up)

fastboot -i 0x1949 flash unlock 0xFILLIDSERIAL.unlock

(replace the filename with the file you created from cuberHDX.py, once done should show successful in green letters)

fastboot -i 0x1949 reboot

(cross fingers)

Install CM12

http://xdaforums.com/kindle-fire-hdx/development/rom-cm-12-unofficial-apollo-thor-t3050199

Put cm12 rom into a directory (I make a roms folder on the internal card), reboot into TWRP, install cm12 rom.

Install gapps from here

http://d-h.st/users/dhacker29/?fld_id=27426#files

I used this latest version, gapps-lp-20150211-signed.zip

Huge thanks to everyone who has put their 2 cents into what to do from the various threads all over this forum.