I second Isae, too, they are probably not chronological, though there’s not really any evidence that proves it or its opposite, anyways. I suppose what you’re saying about events differing form world to world is somewhat implied in the series too, and yes, I also suppose that some worlds not shown to us may have had drastic differences, yes. But the worlds that give the clues as to what’s really going on and have some of the characters that are related closely to the plot or to certain events certainly are the most important ones to show, which is what has been shown to us. There could be some side stories or something, describing a world with a completely new chain of events, though I guess except for maybe expanding some more some of the characters who haven’t been the protagonist for any of the arcs, they wouldn’t offer much clues to what’s really going on.