Change file to CS6

That's not something you can do directly on the iPad, but you can export the document as an .ai file or a PDF. Go to Publish and Export, choose either Quick export as Ai or Export as > PDF.

It's possible one of those may open in CS6, but to be sure, you can back-save as a CS6 file in desktop Illustrator.

Open either file in desktop Illustrator, choose File > Save As... and in the Illustrator Options dialog, under Version choose CS6. Some art may not remain as vectors, like anything created with the Repeat feature on the iPad because it didn't exist in CS6.