[Sony Xperia 1 III] Forbesii:
Things needed:​

1. An Xperia 1 iii (of corse)

2. A Windows PC (I don't know if there's a Mac or Linux version, but I didn't find it)

3. A reliable USB-C cable

4. NewFlasher

Download: [TOOL] Newflasher (xperia command line flasher)

5. XperiFirm

Download: Tool Archives - XperiFirm Tool

!!!FIRST THING FIRST!!! BACKUP EVERYTHING IMPORTANT

FLASHING A PHONE MAY CAUSE DATA LOSS. PLEASE MAKE SURE YOU HAVE A BACKUP OF YOUR DATA.

1. Download and unzip the XperiFirm and select the ROM you want in the Available Firmware list and download.

View attachment 5396817View attachment 5396819

2. Once downloaded, unzip the NewFlasher into the ROM folder.

Your folder should look like this:

View attachment 5396821

3. Start a command line in the ROM folder and run "newflasher set_active:a" otherwise your phone will boot into a bootloop.

View attachment 5396823

4. Power off your phone and plug it into your PC. Hold the volume down button and the power button until the LED turns GREEN.

5. Now you can double click on the newflasher.exe in your ROM folder and follow the guide. You can keep user data while flashing, just pay attention on the instructions on the Newflasher.

6. Don't disturb the flasher while it is working. Your phone will automatically turn on after the flashing is completed.

My Xperia was purchased in China (XQ-BC72). I have tried many ROMs like Hong Kong and Taiwan versions. Recently I flashed my phone with the XQ-BC62 ROM and everything works very well (mobile data, voice calling, data roaming, dual SIM, exposure alert, etc.). However, I haven't try VoLTE because my carrier doesn't support it (SO SAD).

I'm in Canada and my carrier is CMLink. The data icon for LTE shows 4G if you're curious.

The DRM is not damaged that the Windvine security level is still L1 so you can still enjoy the HDR content on Netflix after flashing using this method.

UPDATE Sept. 28, 2021​

I flashed my XQ-BC72 back. I have several issues while using the XQ-BC62 ROM.

The US ROM doesn't include my carrier's configuration so VoLTE, VoWiFi, showing LTE instead of 4G is not working. According to other threads, T-Mobile doesn't have the configuration as well and someone mentioned only Google Fi users can get a configuration (NOT SURE).

Actually, I didn't find any difference between the XQ-BC62 and the XQ-BC72 ROMs (I'm in Canada).

Although the phone is working fine, the LTE is auto-disconnecting every 30 seconds, while HSPA+ doesn't have this issue. I don't think it's my carrier's problem because I bought a new Fido sim card and it's still disconnecting until I flash it back. So if your LTE works fine, please share your solution down below if you don't mind.

I have heard that the new update 61.0.a.11.92 is enhancing the network performance. I don't know if it's because I didn't update my phone. I don't wanna "play" with my ROM since this is my daily using phone.

Thanks to DennisDD78 who discovered that the OTA is not available if a non-native ROM is flashed, even it's all XQ-BC72. Still, if you make your OTA work, please share your solution!

UPDATE Nov. 26, 2021​

I didn’t update the post due to the heavy university work (so sad).

You can keep your data during flashing now by simply choose an option while flashing, as the Newflasher is up-to-date. But still please backup your important data before flashing.

I can confirm that Gpay and android wear work perfectly after flashing, even a cross-model flashing.

Flashing a different rom doesn’t bring any carrier feature like VoLTE and VoWiFi, see this post.

I also tried XQ-BC62 roms again and also XQ-BC52 roms. Same issue, LTE disconnects every 10 seconds, and it brought no new features at all. I haven’t tried those Japanese roms. If you have any experience, please share.