How do you organize caching on the site?

Question

Search Engine Optimization

Do you mean ETag or LastModified headers for html pages
1. Do you use them?
1.1. If so, which one and for what purpose (separate document, list), and what values ​​do you use
1.2. If yes, then for search bots, how do you use it - the same as for people, or differently
2. How do you reset the cache when changes are made on the site
2.1. Changing the design
2.2. Changing the menu, etc.
2.3. Changing the content of a document or lists
That is, I'm interested in how to set up smart caching on the site so that the cache is reset as rarely as possible.
And another question about search engines - if there is a document and they cache it, is it necessary to reset the cache for the bot, if only the menu or other service blocks have suddenly changed?
Preferably without being tied to any engine

Answer 1

https://symfony.com/doc/current/book/http_cache.html