BE CAREFULL TO READ THE BELOW BEFORE ANY UPGRADE.

The NEW software of Z3 (that starts with R452H6_G_.... ) includes two new functions:
1. Bluetooth could be set as "Always Discoverable" in addition to "3 minutes" or "OFF"
2. Under tools, a New "Notes" application exists to allow chating text messages over the Bluetooth


BEFORE any upgrade:
Do check the Software version AND the flex model (underneath the Battery):
if the flex model is:

HG00154 or HG00153, then check if the software begins with R452B_G_... or is exactly R452H6_G_08.00.05R_B. If yes, you can flash the 1FF in R452H6_G_08.00.05R_B_LP34_HG00153007_1FF.zip  or R452H6_G_08.00.05R_B_LP32_HG00154007_1FF.zip
   
HG00710 or HG00709, then check if the software is R452H6_G_08.00.05R. If yes, you can flash the 1FF in R452H6_G_08.00.05R_LP32_HG00710006_1FF.zip  or R452H6_G_08.00.05R_LP34_HG00709006_1FF.zip

For any other combination for software and flex, do NOT flash the phone with R452H6 software, otherwise the phone will be dead.

In summary:
R452H6_G_08.00.05R software should be used for phones which are preloaded with R452H6_G_08.00.05R and have model numbers: HG00710 or HG00709. 

R452H6_G_08.00.05R_B software should be used for phones with R452B_G_... that have model numbers: HG00154 or HG00153 to cross flash to R452H6_G_08.00.05R_B  so that these phones can support the new features discussed above.

Not following the above may damage the mobile / risk the mobile not powering-up. BE CAREFULL TO READ THE ABOVE BEFORE ANY UPGRADE.