I'm being a bit pedantic but

> Misconception: "The browser decides to send cookies."

> Wrong: A browser, or user-agent in general, will never invent a cookie out of thin air, and therefore it never sends a cookie unless it has been set by the webserver beforehand (either with an HTTP header 'Cookie' or with JavaScript code).

These statements are not mutually exclusive and are in fact both true. Browser would not "invent a cookie out of thin air", but it also "decides" to send a particular cookie and there are various configs, switches and decisions (either directly in browser code or extension) which determine if cookie gets sent.

Other misconception answers sound right to me.