Hello,
1. there is a setting to define it per URL:
"Custom alternative language pages"
Specify alternative language versions for your pages: enter your page URL followed by a list of language identifier with alternative URLs, example:
[ External links are visible to logged in users only ]
de [ External links are visible to logged in users only ]
es [ External links are visible to logged in users only ]
2. sitemap is created from the scratch each time.