i have successfully updated my L1520(RM-937) to denim in india with the help of Launch Nokia Care Suite and navifirmplus. and it's working file.
steps
download Cyan firmware using Navi
download and install Nokia Care Suite
put downloaded firmware file in "C:\ProgramData\Nokia\Packages\Products\RM-937"
and follow instruction given @ [Tutorial] Unbrand (flash) Nokia Windows Pho?€? | Windows Phone 8 Development and Hacking | XDA Forums
screenshot coming up....believe me i am loving it...Hey Cortana
steps
download Cyan firmware using Navi
download and install Nokia Care Suite
put downloaded firmware file in "C:\ProgramData\Nokia\Packages\Products\RM-937"
and follow instruction given @ [Tutorial] Unbrand (flash) Nokia Windows Pho?€? | Windows Phone 8 Development and Hacking | XDA Forums
screenshot coming up....believe me i am loving it...Hey Cortana