How to relaunch a website without damaging SEO?

Question

Search Engine Optimization

1. There is an old site that is over 10 years old.
2. It is planned to update the site (design, layout), while the content of the site (articles) will remain the same.
Now the question: In connection with the update of the site, the URLs of the various pages of the site will also be updated! What steps should a developer take so that after changing URLs (after updating) pages that have been indexed by search engines over the past 10 years (old URLs) are available?

Answer 1

Make the transfer as follows:
1- make page-by-page 301 redirects from the old URLs to the new ones
2- all pages that are not on the new site, but are on the old redirect with a 301 redirect to the main page of the new site or page by page to the page that matches the most in meaning (the second option is better, but more time-consuming)
3- if possible, transfer the old title, description and h1 page by page to the new site (if there are no obvious jambs)
4- also, if possible, save the content and its layout
This will be enough.