I have some questions regarding SaaS backup for Office 365 that i didn't find in the documentations
I have moved your post to the new SaaS Backup forum.
Please see if this FAQ post answers your questions?
Veritas will run a backup every 3-4 hours daily and guarentees at least one full tenant backup per day. The backup is only technically 'triggerd' if a new connector is added, otherwise it goes with the 3/4 hours if it is an existing connector. As a result, the backup cannot be performed manually unless it is the first time you are adding a connector.
Regarding the "Automatically add new accounts..." SaaS Backup will periodically check with Microsoft to see if any new acccounts were added to o365. If a new account is detected, the new user is immediately included in the next backup.
You are correct on the last point, point in time restore will allow you to select a specific-date version of your file.
Let me know if you have any additional questions!