Connect the phone to XS++ v3.1 and when it ask you if you want to upgrade the CID to 52, press the Yes button. About firmware version: any firmware will be fine if it's equal with or greater than R1ED001 and the branding is the same, and of course it's need to be CID52(e.g. if you have a Vodafone branded phone use a Vodafone branded firmware).