For sync changing password will clear all previous sync and if they don't match the default Desktop they were saved on then any changes would be gone. Sync pswd reset will change all other devices and what they sync to the new settings of the main sync device or computer they come from. Doing Factory reset on let's say your Laptop or Desktop back to factory condition and the using Firefox sync will wipe they sync clean of all previous saves data. So unless you use the Firefox links to save bookmark/data they will not be there after a factory reset as sync will clear all data when you sync to match current configuration from the computer it syncs from. At this point unless there is by sheer chance another device still holding onto the sync data that is the only way to get back if possible the lost data but if not then they are gone at this point.