Unfortunately, due to limits with the Z-Wave chip and various countries' legal requirements, the frequency and region of a Gen5 product can't be changed by changing a device's firmware.
The firmware does tune the frequency usage of a Z-Wave device, each Z-Wave module has a physical SAW filter installed upon it. This SAW filter hardware defines and improves each device's signal-to-noise ratio (noise from other frequencies) of a specific frequency. In doing so, it also prevents the changing of a Z-Wave frequency upon any device.
Please note that upgrading a device using the improper firmware region may brick the Z-Wave chip, rendering the device broken and voiding its warranty.