Using Open XML SDK for Office 3.0, Which versions of Word documents can be modified?

Question

I read in the documentation (https://learn.microsoft.com/en-us/office/open-xml/about-the-open-xml-sdk#open-xml-sdk-for-office) that,

The Open XML SDK provides the namespaces and members to support the Microsoft Office 2013.

This means, using Open XML SDK, I cannot modify any *.docx files? How can I check whether this document belong to older version of MS Word or not?

Background: I am creating a console app using C# to edit footer of MS Word documents on MAC

Answer 1

The Open XML SDK can open files created with the Office Open XML file formats, which includes .docx files, so the Open XML SDK can open any .docx file.