[T-Mobile Galaxy Note 4 General] AlkaliV2:
I just successfully downgraded from COD6 back to NK4 in order to alleviate concerns that downgrading back to Kit-Kat was going to be an issue. Reference post found: HERE. I am outlining the method I used to downgrade below, but this can also be a guide on how to upgrade to later firmwares.

I don't recommend trying to downgrade past NK4 and only downgrade if your dev says you need to! downgrading is risky and can brick your device! You've been warned!

Downgrade to NK4

or

Upgrade to COD6

1.) Download Odin v3.09

2.) Download full Odin NK4 (Found HERE) or COD6 found, almost everywhere

3.) Unzip the file and there should be a file called "N910TUVU1ANK4_N910TTMB1ANK4_N910TUVU1ANK4_HOME.tar.md5" or your COD6 tar called, "N910TUVU1COD6_N910TTMB1COD6_N910TUVU1COD6_HOME.tar.md5"

4.) Open Odin v3.09 and click the button labeled "AP" and locate the tar file you unzipped

5.) Let it load, it will freeze for some time while checking the MD5 and then be ready to go

6.) Turn off your phone completely; after it is powered off hold vol down+ home + power until you see a warning message

7.) Hit Volume up to continue

8.) Plug in your device and and the it should light up blue under "ID:COM" and say something like "COM:1"

9.) Check to make sure your tar is loaded into the AP slot.

10.) Ensure that they only two boxes that are checked are: "Auto Reboot" and "F. Reset Time"

SHOULD LOOK LIKE THIS PHOTO: http://cdn.droidviews.com/wp-content/uploads/2013/05/galaxy-s4-odin-flash.jpg

11.) If you've verified that your Odin looks like the picture then click "Start" and be patient

*****************************************************************************************************************************

***If Downgrading You MUST wipe USER DATA following the steps below or your phone will boot loop on restart!***

***If Upgrading I

Strongly Suggest

wiping USER DATA to avoid potential issues from upgrading!***

*****************************************************************************************************************************

12.) Wipe User Data as outlined below by booting into recovery as soon as the download completes by holding power + volume up + home until it says, "Recovery booting" in blue in the upper left corner.

13.) After doing the factory reset and rebooting it will you can setup your phone like normal

These are the same steps if you want to upgrade with Odin, you just use the full tar of the upgraded firmware (COD6 in our case)

To Wipe User Data

1.) After you've clicked start and the file completely loads on your phone it will reboot and immediately enter recovery

2.) It will show and Android and a blue bar scrolling across setting up your system. It will reboot again after this

3.) As soon as the screen turns black hold vol up+ home + power to enter recovery again

4.) It will boot to the Android again and you should see THIS before the menu loads

5.) Scroll down to "factory reset/data wipe" with the Vol Down button and then hit the power button to select it

6.) Scroll down again and hit "Yes" so that it completes

7.) After it is done reboot and allow your phone to boot normally

8.) Setup your phone like normal

Done!