When backing up your data, you can include the following ‘group’ tables in the backups, relating to Salesforce objects
The key reason to backup these objects up is to ensure there is a complete audit of data, to help you meet your compliance and industry regulation requirements.
Yes - but via FeedItems (*See below)
In the event of a data loss or corruption restoration, the sharing rules, including Apex Managed Sharing, will be recalculated (please see this article for more information). This will in turn restore the missing share records generated by Apex Managed Sharing and an import would not be required.
Navigate to the Backup Exclusions tab, in the Backup Exclusion Rules table, hover over the exclusion rule relating to the sObject you want to include in the backup, click the X icon to remove the exclusion rule.