Has anyone been dead and then alive again?

When a person's heart stops beating they are officially considered to be dead. A great many people have had their hearts stop beating and then start beating again (as a result of medical intervention in the form of cardio-pulmonary resuscitation or by use of a defibrillator) so they technically have been dead and then alive again. Death can take more extreme forms. When a person has been dead for any prolonged period of time, and the body has decayed, or has been embalmed to prevent it from decaying, then there is no returning to life. That kind of death is permanent.

Of course, for those who believe in The Bible - and I know you are out there! - there are people who have been magically brought back to life. Jesus Christ is said in the bible to have died on the cross and to have magically returned to life 3 days later. There are other cases, Jesus is said to have brought a person named Lazarus back to life. Whether such reports are believable, is really up to you. But even if such things did happen 2000 years ago in biblical times, they have not been observed recently.