Go to Appearance > Customize > Footer to setup footer layout and back to top button.
If you want all pages to use the same footer: Select Footer and choose a footer for all site.
In case there is still a special page currently using another footer, you need to remove that footer currently used in the special page.
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Go to the specific page to setup the different footer.
Go to edit page and scroll down to the Page Settings section -> Footer Version and select a special footer or remove the footer currently used.
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