Hi mgerio,
Presently there are some service reports in Office 365 admin center, Exchange Online audit logging and audit log reports under every SharePoint site, which help view and check the activities in Office 365. However, regarding a system snapshot used to revert the previous setting of Office 365, we’re sorry that it isn’t feasible to generate this system report.
Generally, the deleted contents will be transferred into recycle bin, and they can be restored in limited time. If the mailboxes are deleted, admin can recover the users from Office 365 admin center (Admin>Office 365>users and groups>deleted users). If the subsite/list/library is deleted, the site collection admin can go to Site settings>Site Collection Administration>Recycle bin to restore it. If the top level site/site collection is deleted, global admin can go to SharePoint admin center to restore it (Admin>SharePoint>site collections>Recycle Bin)
About the setting of the site collection, the audit log report may help us to track it (Site settings>Site Collection Administration>Audit log reports).
Thanks for your time and understanding.
Best Regards,
Mandy Meng