Something that I'm personally wondering about is that prior to the 1.2 patch, with Wonder Trade data and stuff we could see a part of the game's code, if I remember correctly.
As you can see on the bottom, some moves are listed with "???", more specifically, moves number 591, 592, 593, 607, 610, 614 and 615, leaving us with a total of seven unknown moves. These are most likely event moves, similar to V-create and Techno Blast and so on from BW. Now, we already have Happy Hour and Celebrate on the list with their index numbers, leaving us with a total of 9 event moves with 7 of them being unknown and Hold Back not having a familiar index number.
Now, I think I can tell what some of them are. The first three are most likely Steam Eruption, Hyperspace Hole and Diamond Storm, Volcanion, Hoopa and Diancie's recently leaked signature moves, respectively. The fourth one may very well be Light of Ruin, another move which is shown in Hotel Richissime's Room Service job in Lumiose City. The next one is probably Hold Hands, which is an actual move as I have gotten it to appear on Hotel Richissime's move list after a few SRs, that leaves us 5 familiar out of 7 unknown. Since Hold Back's index number is unknown at the moment, we don't know if it's one of the unknown two or not, but if it is, that leaves us with one unknown move, if not, it leaves us with two.
