How to restore functions.php to undo all the changes I have made?

I am working on a woocommerce website where I have made some changes in the functions.php page. As the my-account page is not working, so I would like to undo all the changes I have made within the functions.php. I believe that there must be some way to undo changes based on a specific time. As I have made changes since yesterday, So I would like to undo all those changes such that all my code stay available to me just like it was before my changes.

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