Galaxy S5 SM-G900F programmed as SM-9006V I have a Samsung S5. On the box, on the sticker inside the unit, checking the IMEI and using CPU-z they all said the unit is an SM-G900F and is using the Snapdragon core. 

My biggest problem with it is I want to be able to back the entire unit up so that if I mess it up, I can put it back to its original state. There is no simple universal backup method, so I used ADB to do the following command:

dd if=/dev/block/mmcblk0 of=testsystem.img


I made changes to the programs and did this command:

dd if=testsystem.img of=/dev/block/mmcblk0


I thought this worked, so then I proceeded to try to install Cyanogen ROM. After many tries and other things too tedious to describe about what did not work, I finally got this version to work:

13.0-20160114-NIGHTLY-kltechn


This version and ones before it are for the SM-G9006V Chinese model, not my supposed international model. I tried to put in this version:

cm-12.1-20151007-SNAPSHOT-YOG4PAO333-klte


which should work for the SM-900F but it won't.

Now trying to put the phone back to its original state using

dd if=testsystem.img of=/dev/block/mmcblk0


does not work.

I think the phone was programmed somehow with two different ROMs, and I am hoping someone can tell me how to do this, or why I can't make dd command work?



Here is some more information before I did anything to the phone:

On Kies before changing to cyanogen rom it said it could not update the phone and reported the following:

G900FXXU1POEC/G900FOJV1POF1/G9006VZNU1BOE3/G900FXXU1POEC  (XSG)


Original answer to *#1234# before Cyanogen rom was:

G900FOJV1POF1


Now this information cannot be gotten from KIES, and the *#1234# no longer works.

In addition, I wrote down all the following from the phone in its original state:


Device Name: Galaxy S5
Model Number: SM-G900F
Android Version 5.0
Broadband Version: G900FXXU1POEC
Kernel Version: 3-4.0-4884557     dpi@swdd5702 #1  Tue May 12 11:54:06 KST 2015
Build Number: LRX21t.G900FXXU1POEC
United Arab Emirates   TRA ID:0016333/03  TP: 00000000/00
Security Software MDF V1.1 Release 4   VPN V1.4 Release 3
Knox Version   Knox 2.3


Standard SDK 5.3.0
Premium SDK 2.3.0
Customization SDK 2.0.0
Container 2.3.0
IM 2.0.0
CEP 2.0.1
Enterprise Billing 1.0.0
SE for Android 2.2.1
SSO 2.1.1
TIMA 3.0
VPN 2.2.0



I want the phone to have a complete back up that is simple like using dd.

I want to use the phone in the US and Asia.

I would like to be able to put it back to its original ROM programming.
Current Situation


I am afraid you have messed up things in a big way by flashing a ROM not meant for the device ,see this to get more understanding Can I install a ROM made for a different device?
Also surprised that you were actually able to successfully install CM meant for another device
I am not conversant with "dd" commands, but the probable reason it is not working now is that the partition information has been altered after flashing the wrong ROM 
Samsung phones do not come with two ROMs as you are speculating based on Kies output. One remote possibility that strikes me is that this is a refurbished phone which had traces of earlier ROM (if that is possible ), leading to Kies reporting inability to upgrade. You can verify, if your phone is refurbished or not and also obtain more details about your phone, see my answer How can I tell if my phone is refurbished


Next Steps


At this juncture, trying to solve things on your own may cause more damage than help, so  visit a service center to get it fixed. Leave it to the experts
If you still want to experiment, download correct stock ROM from Sammobile (requires registration) and flash stock using Odin as explained [Guide][Samsung] How to flash Stock ROM   


Edit


OP has confirmed that check by Phone Info Samsung shows it as  refurbished. My guess is that the refurbishment was not properly done in terms of OS, leaving traces of earlier ROM as well. This could possibly disrupt attempt to restore to stock. This complicates situation further and strengthens my earlier recomendation to have the service center handle it. Of course, this does not stop OP from trying to flash stock ROM



  
  On Kies  before changing to cyanogen rom it said it could not update the phone and reported the following:
  
  
  G900FXXU1POEC/G900FOJV1POF1/G9006VZNU1BOE3/G900FXXU1POEC  (XSG)


factually reported by Kies, shows this, which is further confusing, either all the actions done by OP are not correctly reflected or there is an issue with refurbished phone


G900FXXU1POEC is UAE lollipop for your device
G9006VZNU1BOE3 is lollipop for SM-G9006V 
G900FOJV1POF1 is lollipop UAE