A file came with the down load. Looks simple but it says that the keys if purchased, (I have one) will remain stored so you can use it by returning to the latest firmware via Sentinel. So if I update, then roll back I lose the key until I am back up to date?
None of the upgrade keys are affected by rolling back firmware. Any upgrade keys you have entered into the scanner are not stored on the SD card or in the firmware. They are written to a separate memory area in the scanner. The waterfall feature itself (and other upgrade features) are written into the firmware. If you roll back your firmware to a version that doesn't contain that feature, obviously that feature isn't going to be available to use.... but the upgrade keys for that feature are still in the scanner. When you re-install the newer firmware that has the feature included, it will recognize the keys that are still held in the scanner's memory.