No, that box transformed into castle
Most likely
no. and that rainbow kingdom is Cloudsdale.
The Crystal Empire is the Rainbow Kingdom in your Little Pony Friendship is Magic.
Yes, the Twilight's kingdom from My Little Pony Friendship is Magic is the Rainbow Kingdom.
The My Little Pony Friendship is Magic Rainbow Power toys are connected to the box on the Root of the Tree of Harmony show.
Yes, the My Little Pony Friendship is magic episode Twilight's kingdom is involved in the rainbow power.
This information has never been revealed, so I can only guess. I would suggested watching the Season 4 Finale when it is released to find out. In my opinion, the Rainbow Kingdom and the Tree of Harmony box are related.
No information has been revealed as to what exactly will happen when the box is opened. It is supposed to be a mystery.
Friendship is the pot of gold at the end of the rainbow.
Yes, the official synopsis of the Season 4 Finale hints at the "Rainbow Kingdom".
The Crystal Empire is not yet considered to be the Rainbow Kingdom, but is suspected that is will be designated this title in the Season 4 Finale.
It has been suggested by the synopsis of the Season 4 finale and by press releases from Hasbro that the Crystal Empire is in fact the "Rainbow Kingdom". What this means is unknown.