[AT&T Samsung Galaxy S 4 Q&A, Help & Troubleshootin] JohnMonsour:
You should realy read.... All of us on MF3 know that !!... That was one of the fist ways to boot back up. Safe strap is going to be a savior for you.... Basically this has been discussed a million times..... If you are on MF3 you cannot downgrade you can only upgrade or stay on MF3, If you want 4.3 sooooo bad I will link it for you. But I suggest staying patient. There is nothing really that improved over 4.2.2. So I would advise you not to upgrade but I will post the links and tell you how to do it. One if you were smart you would have made a nandroid backup thru SS and then when you boot into that you stay on the stock rom slot. Hit then go in and write your backup just the system folder.... So you won't lose all of your data. Now if you didn't make a nandroid backup. Then you can try flashing the stock recovery and fixing the permissions thru safe strap..... IF that doesn't work well you are just up the creek.....

HAHAHAHA. JK Get odin and get the MF3 Tar.MD5 files But your phone manually into odin mode and Go back to stock MF3. Seriously read, read, read. I will make it real easy for you this time. By posting links but you are just asking for it. So first grab these files: https://mega.co.nz/#!WEEzSA7Z!aB46731_AwM7P83eMdDlmFYd1hUZfFBcQAZjc1X7wAE These are the stock MF3 files that were contributed to the community by Shockndrop: http://xdaforums.com/showthread.php?t=2502003

Now grab Odin, I prefer this one: ODIN 1.85 http://xdaforums.com/showthread.php?t=1262272

Now put the MD5 files in their proper places in odin and and hook your phone up with a Good **** Solid Universal Serial Bus Cable: Like pitured here:

Put her down into a coma AKA, ODIN Recovery mode manualy by holding power, home, and volume down. Then when prompt after the warning volume up to continue. Flash with Odin to restore to stock MF3. Brand Spaking new!!!!

Use your favorite root Method, New root method is the only one we support here on XDA, Which involves an SD Card,and the Terminal from the Play store. Or if you want the fast and dirty way because you are lazy do the Kingo root, I don't indorse it, but I have yet to hear anything negative about it, other than speculation. Links: http://www.kingoapp.com/android-root/download.htm - one click method Easy.

Old proper way: Quoting Jortex "HOWTO:

Use a card reader to format the micro SD card to exFAT (FAT32 or other formats does not work) in Windows. I haven't tried Linux or MacOS X, so they may not work.

Download the attached file (Root_for_ATTSG4_FM3.rar) http://xdaforums.com/attachment.php?attachmentid=2165629&d=1375669716 and extract it into the root of your EXTERNAL microSD card using the card reader in Windows. (You can do the extraction using WinRAR, http://www.rarlab.com/download.htm or 7-zip, http://www.7-zip.org/download.html ).

Put the SD card back to the phone and download the Android Terminal Emulator app.

Open the Terminal Emulator app and run below 3 commands:

Code:

cd /mnt/extSdCard

./pwn

./script.sh

Then, open SuperSU and check everything looks good.

Then open a root app and it should be working properly.

Reboot your device once to confirm root is still working after reboot.

Come back to the post and press the THANKS button

Notes:

I uploaded a screenshot from the Terminal screen where the instructions are entered. Yours should be the same except you don't need to enter the "ls -l" command. It's just to show what files I have on the SD card. Ignore LOST.DIR directory.

Remove any SuperSU apps from your phone before following the above steps. script.sh installs it automatically.

You can use adb shell instead of a terminal app which is more convenient but requires Android SDK. Follow these steps only if you are about to use adb:

Download and install all Samsung Galaxy S 4 drivers from here: http://www.samsung.com/us/support/owners/product/SGH-I337ZWAATT#

Activate Developer options -> USB Debugging mode. To have the phone show the Developer options, go to Settings -> More -> About device. Tap on "Build number" 6 times.

You have to use an external SD card. No other alternative have been found yet. Using the device storage, i.e. /mnt/sdcard, or /data/local/tmp, DOES NOT work.

Warning (suggested by rushi.1986): "We have root for MF3 but we neither have a working recovery, nor an ODIN back to stock package. Be very careful what you do with your root. At this point, there is no way to recover even from a soft brick. (unless you know exactly what caused the soft brick and can correct it using adb)"

For those who do not know how to format an SD card on Windows (thanks to jee'sgalaxy):

Insert the micro SD into the computer (may have to use a reader or a micro SD adapter).

Go to "My Computer".

Right click on your SD card that showed up.

Click Format.

Choose exFAT as the format.

Click "OK".

Don't forget to press the THANKS button.

Credits:

***Exploit adapted for AT&T by Jortex***

***Original Guide by Open1Your1Eyes0 for Verizon Galaxy S 4***

***Original Exploit by DooMLoRD***

Next install your only way as of now to run custom roms period in your current situation and you should be incredibly grateful instead of saying that you want 4.3 soooooo bad....... really not tooo many benefits at all. Now 4.4 KittyKit lol is a different story..... So grab the latest and greatest version of safestrap from here: http://xdaforums.com/devdb/project/dl/?id=1814&task=get

After Flashing Any Compatable Rom flash these every time Link: http://xdaforums.com/devdb/project/dl/?id=508

They are the MF3 modules you will need them for wifi to work.

Transfer to sd card install just as you would a regular unknown source APK File..... Tick that in settings Security tab. Also hit your build number 20 times to unlock developer options and always have usb debugging on.

Now boot into safe-strap and dump a nandroid backup and you will be good to go. All thanks to the HashMan aka HashCode, And his sexifing SS. Okay now that you have a backup do anything of your hearts content. Just don't be fooling around with the bootloaders code.... this can really turn your cell phone into a paper weight.

Now here is a list of known compatable roms with SS:

Confirmed working ROMs Thanks to graydiggy http://xdaforums.com/showthread.php?t=2428254

Google Play Edition 4.2.2

http://xdaforums.com/showthread.php?t=2356276

http://xdaforums.com/showthread.php?t=2341376

Deadly Venom

SHOStock

Darth Stalker

Graviton (Installs fine for some, will not install for others)

Goldeneye (May have issues)

Wicked ROM (T-Mobile) Input correct APN and change network mode to Auto LTE/GSM Will most likely lose root.

All Infamous TW Roms should work

Input correct APN settings for non AT&T ROMs (ie i9505 ROMs) to get LTE

Omega ROM i9505

Echo ROM i9505

Vision X i9505

BoBCaTROM i9505 (May not need to change APN)

Hyperdrive ROM. (May not be able to send SMS while on LTE)

Grab one create a rom slot and flash to your hearts content.

As for the 4.3 Odin files...... I think you can find them yourself it would be ignorant for me to post them for you.