There is no way of knowing for certain until the episode comes out, but it seems to be a strong possibility.
She already did. Fluttershy got her key in Season 4 episode 16 "It Ain't Easy Being Breezies."
In the final part of the episode, A flash is rainbow is visible in Fluttershy's eyes, suggesting, as per this pattern of flashes of rainbows seen in previous episodes, that Fluttershy had recieved her key. It is not yet known what purposes these serve.
No. Justin Bieber was never cast for the television show My Little Pony: Friendship is Magic.
Fluttershy confronts a dragon in season 1 episode 7 "Dragonshy"
My Little Pony Friendship Is Magic - 2010 It Ain't Easy Being Breezies 4-16 was released on: USA: 1 March 2014
Andrea Libman .
It might be, as it does center on Fluttershy, but we have no way of knowing for sure until the episode comes out.
Most likely, yes. Synopses have been released for all episodes in season 4 other than the final two which, based on episode 24 being the Equestria games, will probably be a two part finale. No episode between now and then will center on Twilight, so that puts the finale as the time when Twilight will likely get her key.
The My Little Pony Friendship Is Magic episode with baby twilight sparkle is calledThe Cutie Mark Chronicles"this is where the cutie mark crusaders ask twilight applejack fluttershy rarity pinkiepie and finaly rainbow dash (not in that order exept for rainbow dash she comes last)
Season 1, Episode 1: Friendship is Magic
Yes, Cadance will appear in the My Little Pony Friendship is magic episode Twilight's kingdom.
By episode: Rarity: S4 E8 "Rarity Takes Manehatten" Rainbow Dash: S4 E10 "Rainbow Falls" Pinkie Pie: S4 E12 "Pinkie Pride" Fluttershy: S4 E16 "It Ain't Easy Being Breezies" Applejack: S4 E 20 "Leap of Faith" Twilight Sparkle: S3 E26 "Twilight's Kingdom Part 2"