As time moves forward in the new year, so does the adventures. Everything that seasons 5 and 6 has shown us will be altered in this timeline with the presence of Discord and Sunset Shimmer. New scenarios, same faces, different outcomes.
This is a sequel towards Anon-A-Miss: Friendship is Magic. Now it's with Twilight and her friends.
I won't detail every episode in season 5 & 6. Just some that are crucial within the timeline.