You need to be within your free update period to be able to be able to re-download your software back . Even if you have a scan folder backup and you are out of your free update period, don't think you can perform a factory reset and copy and simply paste your scan folder backup back to ES Explorer and be able to access Diagnostics until you access  Autel's server and it confirms the tablet to be within it's free update period. Guess you are only limited to Cherry picking certain car apps from your backup to try and attempt repairs if one of the car apps software gets corrupted and needs to get deleted. Don't do a factory reset unless you want to buy an update and start off from scratch!