It's already discussed elsewhere on the main pages, but if one is familiar with the game series (or even just Victory), Plutia's appearance makes no sense. In fact, by the game's metaphysics, they're mutually exclusive - one's a goddess (Neptune being born as one or Plutia getting a CPU Core), the other lives and dies as a human well before the era of the show.
Except that this Plutia is also from another dimension. Also, if you get Victory's true ending, Ultradimension!Neptune appears in voice only.
And let us not forget that Ultradimension!Nep is very much alive and well even after Victory, as she shows us herself in VII.
The end of the treaty also means that they are once again at war. Naturally, this brings all the Unfortunate Implications being in a war has, with forbidden transport between nations, no cooperation, and even the whole friendship thing will fall by the wayside as they slowly ramp up the war efforts, or even if they keep them at current levels. Problem is, international events or everyone being friends together again can't happen anymore because of the politics involved in the loss of the treaty and the restarted war, leaving it not such a happy ending after all.
Not necessarily. By the time Neptune makes the announcement annulling the treaty, they've become Fire-Forged Friends, hence her decision that it wasn't really needed anymore, and the others seem to agree. After everything the goddesses went through together, they probably realize by that point that restarting a war that didn't resolve any of their issues before isn't a good idea or good for their nations. Any conflicts that do happen is probably going to be more in line with a sports rivalry, to see who's the best in a fight, but not likely all out war. Worst case scenario, chant the MST3K Mantra...
In the final episode, they destroyed the Pong Laser by playing Pong with Neptune's body.
Uni scores three successful hits on Arfoire in episodes 4 - 5, the highest of all the characters at the point of time. All three of them targeted her wings.
Unfortunate Implications being in a war has, with forbidden transport between nations, no cooperation, and even the whole friendship thing will fall by the wayside as they slowly ramp up the war efforts, or even if they keep them at current levels. Problem is, international events or everyone being friends together again can't happen anymore because of the politics involved in the loss of the treaty and the restarted war, leaving it not such a happy ending after all.