[Nokia Lumia 920] paulday:
I have successfully installed the AT&T Amber Developer rom to a brand new Locked Black AT&T branded phone just delivered this morning from AT&T. I had to go with AT&T to make sure that I got model rm-820 to ensure complete compatibility with 4G/Edge. The phone is locked, but I'm waiting for an email from AT&T to unlock it.

Here's how I got it done, just took some time and a lot of patience. As a bonus, I also got internet sharing working, without calling 611 and having tethering turned on, here in the NE USA, on AT&T's network.

Please remember that this is for a BLACK phone. Adjust for different colors if possible.

Download and install the latest version of NCS.

Download Navifirm+ v2.3 here: http://www.symbian-toys.com/navifirm.aspx. No need to install, just run it when you need it to download the rom.

I only downloaded two roms:

Rom 1

The first one was the pre-portico Rogers rom. I downloaded the needed files from here: http://wp.it168.com/thread-217624-1-1.html

Download the files under this heading "059Q6W4: RM-820_Rogers_Canada_VAR240202_v2_Black" by right clicking each one and saving to C:\Program Data\Nokia\Packages\Products\rm-820. Remove the check-sum numbers from the front of each file name when the downloads are complete.

Rom 2

Use Navifirm, or any of the other means, to download rom 059R2L5 RM-820 AT&T DEVELOPER DEVICE BLK. Copy the downloaded files to C:\Program Data\Nokia\Packages\Products\rm-821.

Flashing the roms

Start NCS and open product rm-820. Select Rom code 059Q6W4 RM-820_Rogers_Cana... Version 1232.2109.1242.1002. That should be the only one there. Click the start button to flash the rom to the phone. Ignore the warning about it not being the correct rom.

When flashing is complete, setup the phone just enough to get to the settings. Connect to your WIFI. In settings, go to Phone Update and click on Check for Updates. Keep tapping on the phone to keep it awake though out this procedure. The phone will take forever to find, download and install the first update. When completed and the phone is reset and on, set WIFI and check for updates again. Follow the same procedure until you are told that there are no more updates. I believe that it was 3 updates, maybe 4. Be sure that your WIFI is enabled each time to prevent failure of an update.

Go to NCS and open product rm-821. Select Rom code 059R2L5 RM-820 AT&T DEVELOPER DEV... Version 3047.0000.1326.20... That should be the only one there. Click the start button to flash the rom to the phone. Ignore the warning about it not being the correct rom.

Enable internet sharing

When the installation is complete, setup the basics of the phone. Enable WIFI. Go to Setting/Access Point and select AT&T - LTE 2 - Lumia.

Go to Settings/Keyboard. I kept the English keyboard and removed the French keyboard. Click on add keyboards and select Spanish (Spain).

Turn off your phone. Turn on your phone and go to Settings/Phone Updates and check for updates. Once the Spanish keyboard is installed, turn off the phone and then turn it back on. No need to do a reset.

When the phone is back on and up fully, go to Settings/Internet Sharing and turn it on. You'll see a screen stating "Sharing your cellular data connection over WIFI... a Broadcast name and password lines. Already had two tablets going thru it as a test. Worked great. Also, go to Settings/Speech and select the language you want spoken to you.

Hope this helps everyone out. I didn't include how to use NCS, feel free to add that if someone wants to.

PS The AT&T rom failure mismatch platform message, which has kept everyone from installing AT&T dev rom, or even own AT&T's rom, onto AT&T branded phones is misleading. What is being checked is the first section of the VERSION NUMBER. AT&T update needs to see at least version 3047.0000... (Amber) of the Rogers_Canada rom on the phone you're flashing the rom to in order to be successful. AT&T also checks a kernal version, which is the same for AT&T and Rogers roms.

By installing 059Q6W4 RM-820_Rogers_Cana... Version 1232.2109.1242.1002, which is the only rom that will flash onto an AT&T branded phone, and updating, you're bring the phone version up to 3047.0000.... and now 059R2L5 RM-820 AT&T DEVELOPER DEV... Version 3047.0000.1326.20... will install successfully.

The phone is now working fully, without any issues that I've been able to uncover yet.

I welcome any and all comments.

Added observations:

To avoid connectivity issues flashing, be sure to use a 2.0 USB port, directly to your computer, NOT thru a USB hub. If you plug into some 3.0 USB ports or a USB hub (powered or not), NCS will see and read the phone, but will fail at flashing.

All files for a rom need to be kept in their separate directories for clean flashing! Best practice is to download the files to a directory named after the rom you're downloading. Rename the directory of the rom you want to burn to your model (rm-820 or rm-821) before starting NCS. I believe Navifirm+ v2.3 already handles downloads this way. Failure to do this can result in a goofy acting phone, missing/not working right features and other possible issues.