Lumia 800 & 710 – Experiments
Full Unlocked ROMs
& Unlocked Bootloaders

The recognised xda-developer biktor_gj has found a flaw and made the WP7 Root Tools “working fine” on Lumia 800 also. Well speaking simply is that a “Full Unlock” for Nokia Lumia 800 is now available as well as for Lumia 710. However it is labelled as “Very Experimental” and you have to be “Careful”. “Interop Unlock” had already been available for Lumia devices previously but this “Full Unlock” will allow full access to the file system and the registry through out the system that many users and geeks welcome this opportunity of installing unsigned apps –which are not in the Marketplace- independently. This also leaves operating system vulnerable and exposed to potential malwares because only the Marketplace is the place where users can get authentic and signed apps which are approved to be used on Windows Phone (like other stores do for their respective platforms to make it secure)

Previous limitation on Lumia 800, not being able to be downgraded, still implies. You can head towards the original thread at XDA forums for more information. See the source below.

[source: xda-developers]