No version of Word has a Revert to menu choice. Word 2016 for Mac has File>Restore, which may be what they were thinking of. Word 2011 doesn't have that command. Here is Microsoft's page about recovering files in Office 2011: Automatically save and recover files
If you set up Time Machine on your Mac, that can be very useful for accessing earlier copies of a file.
When I think I might need access to an earlier version in the future, I use File>Save As and rename the file with an incrementing number or date.