Upgrade Lumia 1320 to Windows 10 Mobile

Due to a lot of requests from people wanting a guide for upgrading Nokia Lumia 1320 to Windows 10 Mobile (it is not officially supported), I have made the following walk through to help you through the process. 

These steps I have figured out after reading multiple posts across XDA and Reddit. While I did piece them together (the sequence of actions), I do not take complete credit for the steps involved (the hows). Feel free to reach out to me @ email in case of any difficulties.

Step 1: Install Windows Device Recovery Tool (link here)

Step 2: Do not connect your mobile phone yet
Step 3: Run the tool and let it update (if any)

Step 4: Once application is up and running, connect your phone (screen unlocked) and let it detect your phone

Step 5: Proceed to complete the recovery and let the phone restart
Step 6: Finish the Initial Setup on the phone to get it running

Step 7: Once the phone starts, verify that you have Nokia MixRadio installed. (If not, you may need to Install Preview for Developers and find the corresponding bootstrap file)

Step 8:  Launch store and disable Auto app updates by switch off 'Updating app automatically'

Step 9: Now go to Downloads and cancel download of 'Extras + Info'
Step 10: Go to phone settings > phone update and check for updates
Step 11: Install the update to get Windows Phone 8.1 (may not be necessary, but it is a combination that has always worked)

Step 12: Keep the phone connected to the laptop and close Windows Device Recovery Tool (if still running)
Step 13: on your laptop go to  'C:\Program Files (x86)\Microsoft SDKs\Windows Phone\v8.0\Tools\Phone Registration' and execute 'PhoneReg.exe'. If this folder is missing you need to install Windows Phone 8.0 SDK (link here) and Windows Phone 8.1 SDK (link here) and retry the step

Step 14: Click 'Register' to register the device (ensure the phone is screen unlocked)

Step 15: Install WPInternals 1.2 (link here)
Step 16: Start up WPInternals

Step 17: Click 'Unlock bootloader' (it will show a message saying phone needs to be in Flash mode; Click 'OK' and let it restart in Flash Mode)

Step 18: On the 'Unlock bootloader' screen, select the following folders

1. For FFU Image - select the ffu file in the folder 'C:\ProgramData\Microsoft\Packages\Products\RM-994' (RM-994 = Product code for 1320 in India)
2. For Emergency Flash loaders, download bin (link here) and hex (link here) files and select the folder where they are saved
3. For Engineering SBL3, do not select anything as there are no SBL3 files available for Lumia 1320

Step 19: Click 'Continue' and let it finish; your phone will restart to normal mode when it completes
Step 20: Download and Save CustomWPSystem (link here)
Step 21: Download, unpack and launch WPV XAP Developer (link here)
Step 22: Ensure screen is unlocked and select and deploy CustomWPSystem via the WPV XAP Deployer

Step 23: Copy MixRadio-bootstrap (link here) to the root folder of the SD Card (this will not work from any other location)
Step 24: On the phone, launch CustomWPSystem
Step 25: Click 'SD Card permissions' and follow instructions to give access to the SD card

Step 26: In 'Select the target app', select 'MixRadio'
Step 27: Click 'Select the XAP' and select the MixRadio bootstrap xap copied to the SD card root folder and select 'Apply XAP'

Step 28: If the app crashes, it means either unlock bootloader did not happen correctly or the xap is not in the root folder of the SD card
Step 29: Launch MixRadio and it should open VCReg

Step 30: Go to templates (the ... at the bottom right corner); select 'Interop/Capability Unlock' and click 'Apply'
Step 31: Download the Custom PFD Registry Editor XAP (link here)
Step 32: Ensure phone screen is unlocked and deploy the xap via WPV XAP Deployer
Step 33: On your phone, launch Custom PFD, go to Registry Tree and Browse to HKLM > SYSTEM > Platform > DeviceTargetingInfo

Step 34: Change the values for the following keys and click 'Write' on each

1. PhoneManufacturerModelName: RM-1089_1087
2. Phone Operator Name: 000-DE
3. Phone Model Name: Lumia 735 

Step 35: Go to phone settings > about & check that the phone is Lumia 735
Step 36: Go to the Store and download & install 'Windows Upgrade Advisor'

Step 37: Run the app and it will schedule the Windows 10 Mobile update 

Step 38: Go to phone settings > phone update; check for updates and you should get the update in a few minutes
Step 39: The first update will get you to W10M Build 10.0.10586.164
Step 40: Once update is complete, go to settings and check for update again. This should get you the Anniversary Build 10.0.14393.448 (as of Nov 25th 2016)
Step 41: If you ever reset your phone, then you will need to redo the following steps to keep getting future updates (since phone will reset to Lumia 1320)

1. Steps 13 & 14 to Register Device
2. Deploy VCReg for Windows 10 Mobile (link here) using WPV XAP Deployer
3. Steps 30 to 35 to set it back to Lumia 735  

That's it. Enjoy Windows 10 Mobile on Lumia 1320 :)