Hi Pedro,
To start, Jetpack Backups are still in development and are only available for sites that are hosted on Pressable:
https://pressable.com/?utm_source=jetpack&utm_medium=site_referral
Do you currently have a hosted site that you want to backup? If so, is the site currently hosted on Pressable?
when is it done (time of the day)? is it incremental? how to restore?
The initial backup will backup your entire site and depending on how large your site, can take some time. After that, however, all of your activity is backed up in realtime and you can revert your site to any activity at any point in time.
https://jetpack.com/support/how-to-rewind/
Where can we get more info about it, like how many restore points?
For more information on backups, please visit our support page:
https://jetpack.com/support/backups/
As you stated, backups require being on a Jetpack plan, and here is information about purchasing a plan:
https://jetpack.com/pricing/
Thanks!