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Martijn's answer is correct. To elaborate: You must include the XML sitemaps on all the sitemaps referenced in that same sitemap. If you don't, Google Search Console will identify return tag errors. Every url in your sitemap that references an equivalent URL on another country's site, must have a correlating "return" URL coming back to the originating pages from tthe hreflang XML sitemap associated with that other country's site.

Refreshing content on the same URL based on the users IP is a very bad decision in terms of international SEO, because Google will see only one of the two versions. What you have to do is, eventually: or change the visible prices and currencies depending on IP of the users (but letting them still being able to change the currency for UX) but not changing the content. or creating a second version (in subfolder for instance) targeting the other market you desire to target. The second one is the best solution Yours is not.