How can i know the charset encoding of a http response?

This question is about charset and is NOT about content-type.

When I make a request to this page - https://www.baeldung.com/java-char-encoding, when I inspect the response, I can see the charset used for the response.
charset as utf-8
charset as utf-8

But when I make request to one of my internal server, i can not find charset info in response.no charset info

Knowing this info is important for me so I can set the encoding type of my HttpClient to same.

1. Now how can i know using which charset the application/json data is encoded. ( i have no contact with the people maintaining the backend. So I have no real person to ask about this)
2. Or not having this info means some default charset is used.
3. If a default is used, does it depend on the http version - 1.1 or 2.0 etc.
4. Any other info I should know/consider

(As these are related Questions, I have ask them in one post. Thanks for understanding.)