I have a 3GS firmware version 3.1 (7C144) that I want to update to firmware version 3.1.2. Is this possible? I don't want to update to 3.1.3 because I want to be able to keep my unlock. The only reason I would like to update is because there are a few apps that require 3.1.2 to work. Should I just leave it and say forget it for now? Or is it possible to update just to 3.1.2?