It is not known what these flashes of rainbow in the pony's eyes is supposed to represent, but this will likely be revealed in the Season Finale of Season 4 of My Little Pony: Friendship is Magic.
No. She does not appear.
It might be, as it does center on Fluttershy, but we have no way of knowing for sure until the episode comes out.
Season 1, Episode 1: Friendship is Magic
Yes, Cadance will appear in the My Little Pony Friendship is magic episode Twilight's kingdom.
Yes, the shining armor will appear in the My Little Pony Friendship is Magic episode twilight's kingdom.
No. It is the last episode of season 3, but there will be a season 4.
Photo Finish is in season 1 episode 20 "Green isn't Your Color"
This episode has already been released.
It's called "Test of Friendship"
Yes. This has recently been announced.
In Pokemon Episode: Season 12: Episode: 24: Pillars of Friendship "If you ever have any questions about Pokemon you just let me know!"
Friendship One, Season 7