Negative English Grammar

Number one would only likely be seen if it were a question. For example:

Let's stop here and get a bite to eat.
No thanks.
Don't you eat here?

It is not unacceptable as an imperative, but just unlikely.

Number two is fine.

Number three is just not something a native speaker would say. There is nothing technically incorrect about it, though.

Number four is correct and it is in fact something a native speaker would be very likely to say.

Hi Setanta,
thank you very much.