Yes, the box on the tree of harmony will be opened in the Twilight's kingdom.
No information has been revealed as to what exactly will happen when the box is opened. It is supposed to be a mystery.
Most likely
No, that box transformed into castle
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.
It is very likely that it will be opened in the last episode, though we cannot know for certain. It is possible, for example, that it could be opened in the first part of a two-part finale.
A pecan tree is in the Plantae kingdom.
Perhaps something relating to it is inside, but it is unlikely that the Rainbow Kindgom itself is in there unless the box is much bigger on the inside that it is on the outside.
The plant kingdom, Kingdom Plantae.
Kingdom Plantae :)
black walnut kingdom
black walnut kingdom
Being a plant, the redwood belongs to Plantae.