Rollback
Updates only ever move forward, so going back to an earlier version means putting a backup back.
Your system takes a snapshot just before every update, named Before update to and the version it was heading for. That is your rollback point.
That snapshot is kept for three days, like every other backup on the vehicle, and is then removed. An update that turns out badly a week later has no snapshot of its own left behind it.
The rollback point is deliberately kept on the vehicle and is never uploaded to the cloud. Rolling back means reading it straight back off the unit, and waiting an hour on a mobile connection to pull a gigabyte back down is no use to somebody sitting in front of a system that will not work. So those three days are the whole window: if a release worries you, try it and decide early rather than a fortnight later.
You are not left with nothing after that. Your nightly backups carry on and the newest one is always kept, however old it is, so there is still a point to return to. It simply will not be the moment immediately before that particular update. See How long a backup is kept.
If the system is still running, open the Sensa Settings panel, choose the Backup tab, find that snapshot in the list and press Restore. See Backups.
If the system will no longer start, follow Recovery instead.