How do you tell search engines that your site has moved?

Question

Search Engine Optimization

The site was on the same domain exemple.com and has now moved to another demo.com
When moving, not only the domain has changed, but also the patch of some pages:
exemple.com/name/prosto-do-bezobraziy-dlinnoe-nazvanie Now it has become
demo.com /name/short-name
Question: How to make it clear to search engines that this site is no longer relevant, and that it should be searched on another domain?

Answer 1

301 redirects should be put on all old pages to new addresses of these pages. You can make one redirect to the site, but page-by-page, of course, is more efficient

Answer 2

On the old host, in robots.txt, specify the main mirror (that is, the new server address)
And add sitemaps.xml to the new one