Currently one new episode is being released every Saturday. As of February 7 there are 14 episodes yet to be released. That would put the finale on May 3 or May 10 depending on whether it is a two-parter and assuming no weeks go without a new episode. A synopsis for the finale may be released 3 to 5 weeks or so ahead of time.
This information has not been revealed yet. In the Season 4 Finale, this information will be available.
Season 1, Episode 1: Friendship is Magic
Yes, the Season 4 finale of your Little Pony Friendship is Magic will be a two partner.
No. There will be a season 5.
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.
There are 13 episodes in season 3.
Season 5 of My Little Pony: Friendship is Magic is the most recent season to be announced. It is set to be released later in 2015. As of February 2015 there is no information about any additional seasons to come.
My Little Pony Friendship Is Magic - 2010 Applebuck Season 1-4 is rated/received certificates of: USA:TV-Y (E/I)
The villain for the season finale has not been revealed. It could be one of them, or it could be someone new.
It is unknown at this time, as it is meant to be a mystery. This will likely be the story arc for season 4, so the contents of the box will probably not be revealed until near the end of the season.
On November 10, 2012!
No. It has been stated that season 6 will focus on exploring Equestria.