I am posting this news on behalf of the the wpinternals author who has requested me to announce the release of this FREE TOOL for this forum.
You can also post questions about how to use the software here.

I will already answer the question in everybody's mind...



This is JAILBREAK + TOTAL ROOT ACCESS... Just like iOS or Android, Jailbreak or ROOT ACCESS does not Sim UNLOCK the Phone.

Direct Quote from AUTHOR's WESITE:

I am proud to announce the immediate availability of Windows Phone Internals 1.0. This tool allows you to unlock the bootloader of selected Lumia Windows Phone models. After unlocking the bootloader, you can enable Root Access on the phone or create and flash Custom ROM's. I created two video's to demonstrate the features of the tool.

Root Access allows you to load your own homebrew software onto the phone with high privileges. Apps can escape from their sandboxes. The tool can also create backup-images of the phone and access the file-system in Mass Storage mode. The tool supports most versions of Windows Phone 8.1 and Windows 10 Mobile. For a complete list of supported phones and Operating Systems have a look at the Getting Started section of the tool.

The download package also contains an SDK, which helps you to easily access the filesystem and registry on the phone from your own homebrew app.

The tool, SDK and video's are available on my new website:

WP internals

I will add more details in this thread soon.

Be careful and have fun!