Preparing for root domain name change in PowerPoint, still some lingering items...

We are preparing to rename our SharePoint root domain using the Powershell script.

It has been asked:

1. Once the rename happens, does it wipe out all the deleted files?
2. Regarding the deleted files that I pulled a report on, a ton were deleted by SHARPOINT\system. We do not have any retention policies in place, the audit shows the same information, not clues there. Any other ways to track down this process?
3. If we create a data room in SharePoint, is it negatively impacted by the rename?

Thank you in advance.