So what happened, then, in 2015, we're given this "alternate version", and this is an appalling, offensive OVA. I'm all for emphasizing story points, arc, plot, and character development, however, 2011 was such a long time that by 2015, we'll have to be convinced that "no, no, there's an alternate version ending and here it is!".
Steins;Gate is a visual novel to start with, so it should have multiple endings BUT that is in the realm of visual novel.
In anime, or manga, there has to be one definite ending, because that completes the ethos of storytelling, you can't just make multiple endings or stories and cash yourself in it, otherwise that rightly states that:
1. This is a milking cash-cow episode.
2. The original creators don't know what they're doing.
There are those who said this is how Steins;Gate should end, and I agree---I very much will like this to be the path or "world line" of the plot, IF THIS WAS what it was supposed to be in 2011. Otherwise, this is a fuck-off piece of 23mins episode wasted. You watch this so you can watch and understand the premise of Steins;Gate 0, and thus you make the creators smile.
The visual novel has four writers: Chiyomaru Shikura, Naotaka Hayashi, Shimokura Vio, and Tanizaki Ouka. However, the writer for the anime version, in the 2011, and this OVA, and on the Steins;Gate 0, is a prick named Jukki Hanada.
It seems that Jukki Hanada realized he could cash Steins;Gate for more, and thus created this abomination, and the "alternate sequel" Steins;Gate 0. Somebody should create a time machine and prevent him from becoming the writer of Steins;Gate anime, at all. Since the visual novel was already established, any competent writer who hopefully won't turn to greed, could do the same thing of writing that he did.
And don't get me started with alternate sequels, for example, I've like Fate/Stay Night so much despite its honest cash-cow arc, but that's because it's on fantasy genre, and it's established that Fate/Stay Night has the Saber arc (the original), the Tohsaka or the Unlimited Blade Works arc, and the Heaven's Feel or Sakura arc. So we accept that as it is; it's an honest cash-cow and we know there has to be THREE storylines of the Fate/Stay Night anime.
But Steins;Gate only has "one" arc, given with multiple endings. And that's a load of bull to put two different endings on an acclaimed anime. That makes it cheap, and an obvious cash-cow loot.
Thus,
The original Steins;Gate is the 2011 version with its 25thepisode OVA, and the Deja Vu movie. THAT'S IT. That's all you need to watch and get along with Steins;Gate as one of the greatest anime of all time.
Otherwise, if you want to contribute to the cash-cow, then watch this appalling alternate version, and its abhorrent alternate sequel called Steins;Gate 0.
