Has there ever been a story where Batman ended up going back in time to before when his parents got murdered and considered preventing it from happening?

Answer 1

I found one occurrence of this so far. In Batman #127 an invention is introduced that gives an individual a chance to change an event and make it as if it never occurred. So Bruce tries it out and makes it so Joe Chill never kills his parents. However they die a few years later in a car accident. Bruce is described as being an indolent playboy, until an incident eventually turns him into Batman. The closing panel shows him and Dick Grayson talking, stating (Dick) "Golly-so even if your parents weren't killed by a criminal, you'd have become a crime-fighter anyway!" (Bruce) "Yes Dick--that's the way it would be! There'd always be a Batman!"

This is additional information if you were wondering how Bruce became Batman in that issue. Bruce is talking with his friends (that's right I said friends, it seems that he is more social with his parents alive) about the costume party later that evening to honor the new Metropolis Airport. Each person is to wear costumes representing flying creatures, Bruce shows up as Superman. A robber and his mob show up causing trouble. The robber looks like Batman and is referred to as the Blue Bat. The real Superman shows up to save everyone and Bruce jumps in to help as well. Bruce gets beat up and decides to take revenge. He later gets the Batman costume and gets even with them. In one panel of the comic he is in front of a mirror in the new costume and covers the lower part of his face and states "I'll devote my life to fighting criminals! This costume that was once a symbol of crime will now become a symbol of justice! As for a name I'll call myself what those policemen called me--Batman!".