Kingdom Hearts hacks have often revealed interesting information about characters or worlds left out of games. We learnt that Woody and Buzz Lightyear were planned as summons for Kingdom Hearts II Final Mix+ in 2007, and that a world based on Disney's The Jungle Book was planned for Kingdom Hearts Birth by Sleep.
Back in September, Youtuber HdHereidme uploaded a 6 minute video showing off a hacked version of Kingdom Hearts 0.2 Birth by Sleep -A Fragmentary Passage-. While no new information or cut content was revealed, we do get to see the entirety of Destiny Islands in stunning Unreal Engine 4.
The video also contains a look at the Mirror Aqua boss battle room, as well as the Upside Down room from the Dwarf Woodland. Unfortunately areas such as Yen Sid's Mysterious Tower were not accessed but we don't have to wait long until we can explore that area in Kingdom Hearts 3, coming to PlayStation 4 and Xbox One in 2018!