Skullkeepa: Um... Vitamins don't work period if you have over 100 EVs in the stat you're trying to increase

DT: It would say it wouldn't work. 10 Vitamins is the max for a stat though, if you're wondering.

But the berries are like reverse Vitamins. The first, if you're over 100 as B~T said, will reduce it to 100, and the rest act, as I mentioned, like reverse vitamins.
Arceus Thing: Currently you can only get Arceus via the movie one, but I expect an event that doesn't come to Canada will have it, as usual. =P And while you can't trade him over the GTS, the GTS isn't the only way to trade Pokemon. if you found someone who had a legit one, you could just exchange FCs and trade it that way.