It also shows which OS versions are supported for enabling Root Access.I would strongly suggest to use the Microsoft / Nokia driver.This section explains some basic information about using this tool.
This bug can be triggered during flashing both with official and unofficial tools and during OS updates and will render the entire e MMC (flash memory) to become write protected.
Engineering phones can be switched to Mass Storage Mode.
In this case it will always be possible to flash a stock ROM to get the phone booting again.
Here is a list which shows what Bootloader Spec was used for different Lumia models.
The earliest Windows Phone 8 based Lumia's are based on the Qualcomm Snapdragon S4 chipset.
For reference I will call the bootloaders of these phones: Later models are based on Qualcomm Snapdragon 200 - 800 series.Qualcomm refactored a significant part of their bootloader-code for these new chipsets.And at the same time Nokia also made significant changes to their parts of the bootloader.Basically you just connect the phone, go to the button.This will download the FFU file and also the emergency programmer files.When in this mode the phone acts as if it is removable hard drive allowing full access to the flash memory. For phones with Bootloader Spec B this is not a problem, because Windows Phone Internals is able to locate all necessary resources to unlock Mass Storage Mode on these phone.