The Petalrain Spring Fairy was released as a weekend egg on April 18th, 2014, along with the Kiss Kiss, Beguiling, and Summer Herald Spring Fairies.
All horses of this color, even stallions, can only be bred once per season. They are currently unobtainable outside of breeding, but will be available through an unknown method sometime in the future.
The Eternal Youth pose was released separately on August 30th, 2014, as part of the Back to School event. It is not currently obtainable through other methods.