[Galaxy Tab Pro 12.2, 10.1, 8.4 General] arcadia2uk:
Update 10/30/2014

There's no need to go back to the "B3" version any longer. The T900UEUANI1 is available on SamMobile, to be flashed w. Odin.

The cf-auto-root listed as "B3" on chainfire's site will work.

Note, I have not created any of this, please thank the original developers in their posts. This is simply a compilation of available info needed to have the most complete and working SM-T900, Samsung Galaxy Tab Pro 12.2.

The sole purpose is to make you save time. However, I'm not saying this will work, and it might even brick your device, but that risk is yours to take. However, it worked for me, so why shouldn't it... Trust the steps, there's a reason for this madness. Believe me when I say it; I've learned the hard way, and it has not been a pleasant journey.

If your SD cards looses necessary rw privileges it seems like not even a backup will correct them, even after wiping the SD cards and formatting data.

If you haven't yet upgraded from B3 to D4, I recommend you to do this first! There are major improvements between the two versions.

1. Rooting:

First flash the P900XXUANB3-RecoveryImg (forgetting this will create a softbrick, and you will have to start over, also use the Odin 3.07, supplied, I have not tested with the later 3.09)

then flash CF-Auto-Root-v2wifi-v2wifixx-smt900

for detailed method and files see: http://androidcentral.us/2014/05/root-galaxy-tab-pro-12-2-sm-t900/

I forgot, it's important to use original cables directly connected to the PC, a docking station connection, or an EOM cable might be a reason for flash failure.

2. install TWRP:

Flash openrecovery-twrp-2.7.1.0-v1awifi

link: http://xdaforums.com/showthread.php?t=2679825

3. disable Knox:

Open SuperSU and answer yes to disabling KNOX

4. fix SD-card issue in KitKat 4.4:

Download and run JRummy's "SD KitKat Fixer" from market. I had no luck with any other comfortable fixing apps.

5. important!:

reboot into recovery and wipe both External and Internal SD, as well as Formatting Data. Don't forget to backup all files you want to keep onto your PC! for later re-installation. I know this must feel hard, but I sincerely advice you you follow this step. Most apps are not KitKat ready, as of now, and won't allow you to download or access the data if you haven't prepared your SD's in advance.

6. init d support:

Download and install Stericson's BusyBox from market

Download and install Uni-init v1.0

link: http://xdaforums.com/showthread.php?t=1933849

7. Flash Player support:

Download and install fixed AdobeFlashPlayer 11.1

link: http://xdaforums.com/google-nexus-5/help/guide-how-to-play-flash-video-android-4-t2548001

If you're using Dolphin Browser, also install the Dolphin JetPack, and modify Settings/Web Content/Flash Player/ to Always On.

8. ADBlocking:

Dowload and flash LATEST_MoaAB_ADBlocking_Super

link: http://xdaforums.com/showthread.php?t=1916098

9. De-bloating:

for de-bloating at a maximum you can disable numerous of the Samsung apps, by pushing the three dots, upper right corner, while in the apps-screen mode.

Also, don't forget to un-check the de-bloated apps from auto-update in Play Store, as well as in the Samsung update if you signed up for this service.

10. (Re)-nstall your apps

You're done, and it's time to restore or download all the apps you need and it will work in KitKat 4.4

None of the modified stock ROM's currently available seem to mount correctly. If something goes wrong, you will most likely loose your SD card privileges. The original T900UEUAND4 stock ROM can be found here: http://www.sammobile.com/firmwares/3/?download=29102. Just unzip and flash with Odin, then start again with step 1.

Also, due to lack of time, I will not be able to monitor this post. I hope you will help one another out with clarifications, or anything I might have missed.

Best of luck,