According to Fahrenheit 451, what is the meaning about freedom of speech?
I'm not sure what you mean by your question, either. I'll take a different angle and interpret as if you're asking what the novel reveals about freedom of speech, rather than what about freedom of speech is contained in the novel itself.
Freedom to read and think and make decisions oneself is primary in the novel. Speech isn't the central issue, by any means. Indirectly, however, one could apply the issue of freedom of speech to the banned books themselves. If books were banned originally, as Beatty tells Montag, because special interest groups kept complaining about what was in books, then the writers' freedom of speech is being denied. One can't please everyone with every book. If the right to write is denied because of special interest groups, then that is a violation of freedom of speech.
I hope I helped.
This question, like the earlier one about freedom of choice, is very unclear. If you could give us a better idea as to what you want to know, we could give you better answers.
I think that Guy Montag and Faber and Clarisse McClellan would probably see free speech about the same way we do today. All three of these people wanted to be free to have their own thoughts and, I think, to express whatever ideas they had to anyone else.
Captain Beatty might see free speech differently. I do not think he would really value it. Instead, he would think that we should be free from hearing other people say things we don't like.
Mildred Montag would probably not think about it much at all. She probably sees free speech as her right to talk to the "family" on the parlour walls.