Do you need to breathe to talk?

Answer 1

No. Although you do need air in your lungs to talk because the air going through your larynx (your voice box) and the vibrations from that going up your throat make noise, breathing is an action implying both inhaling and exhaling. It should be generally understood that someone indicating they cannot breathe are most likely referring to being unable to inhale.

Even when someone exhales as much as they can, there is still air remaining in the lungs, known as their Residual Volume. A person can still speak using this volume of air. Thus, ability to speak is not an indicator of being able to breathe, as inhalation is not necessary for speaking.

Furthermore, someone who is not currently breathing is not necessarily dead. Cardiopulmonary Resuscitation is often used to restore both a person's heartbeat and breathing, which does not actually constitute resurrecting them.