This story has been done to death and this movie wasn't good
In the Flash comics, they did this same story. The Flash goes back in time and saves his mom and comes back to a strange new world.
The Flash TV show did this same story too. The Flash goes back in time to save his mom and comes back to a world that is different.
It was called Flashpoint and there was an animated movie about it. It was called Justice League: The Flashpoint Paradox (2013)
You should watch it.
This movie tried to do this same story but wasn't as good. They had a different older Batman. In the comics, Batman was actually Bruce Wayne's father, so it made sense for him to be older. Why was he older in this film ?
In none of the stories did they ever have 2 Barrys. This movie had so much potential and could have been great but like most DC films, they just can't get it right.