Unless you still have the construction.The proposition 1.6 ROM file somehow, I do not believe the version of the operating system is the problem. I imagine it's lock on the device or carrier, not the operating system.
Check out the answer to this question to see how to view and edit the file build.la proposition. You can report a different / OS version through that device. If you want to change your apparent carrier MarketEnabler test the application.