To view a previous version and the edit history of your story:
Click the three dot menu in the top right corner next to the Save button.
In the dropdown, click "See Version History."
Select your desired date.
To restore a previous version to edit, click 'Restore' in the top toolbar. This will revert any changes you have made to that selected version.
To compare different versions, check out this help article.
To make changes to a live story or compare different versions of edits, check out this help article.