Hi, Probably the least risky way is flashing original firmware and then modifying individual files step by step. So I only need backups of modified files. But it seems, that there are dozens of original firmwares and there is no more official download location? I have the firmware for product code 059J228. But can I use it for an N9 with another code? Or should I buy only a model with same product code? TIA for any hints, Peter