I have a Sumsung Galaxy s7 Edge which is a “live Demo Unit" I have factory restored the retail firmware and it is free of any reference or behavior of the demo unit.
Before you do anything, make sure you have backed up your device to google cloud, smart switch, or Samsung Keis.
Also make a note of the IMEI number and Serial Number if you want to flash a working model. Sometimes these can be erased and will need to be flashed afterwards, although I have only encountered one such occasion this was needed from the dozens of phones I have updated firmware on.
It is relatively easy to restore the device to factory retail state by following the following instructions:
1) Start the device in Android Recovery Mode
2) Wipe cache partition, then,
3) select Wipe data / Factory reset
4) power off device (If you fail to follow steps 1-3 before doing step 4 onward, the process may not be effective)
4) Go to https://www.sammobile.com, find the exact model you have and download the latest firmware for your country. Any Carrier version. Download and unpack zip file. Make sure it is the exact model. If you cant find it, You can be safe using a version that has the “F” immediately after the model. eg: SM-G935FXXU2EREM where F is designated as “Global”.
5) Download Odin software, install it, and run the program.
6) select each of the BL, AP, CP, and CSC options one at a time from the firmware folder. The AP file could take a while to load depending on your computer configuration, so please be patient. Do not select the CSC HOME option. If you do select the CSC HOME option you will have to flash the device again from step 1 because all your apps and user preferences will not be affected and that means many demo features will not be removed.
7) Start phone in Download mode. Connect cable (It is very important that you make sure it is the original Samsung Cable), then press the volume up key to start Download Mode. (If all is correctly done, the Odin log window should show device is added).
8) Click Start in Odin and wait for the process to finish. This will take a while. If successful the box in the top left should go Green and say Pass.
9) disconnect phone from cable before restart completes. If the device doesn’t restart correctly, reboot the device. It should be working just fine. Of course it is now a fresh new system and will need either a restore of your device from google backup to reinstate your apps etc, or setup from scratch.
Everything should work as a new device out of the box with the exception of the cellular service. I use mine as a MINI tablet. works great around town on hot spots for Google, Google Maps, Skype, Whats App, Facebook messenger etc..