Minecraft wiki entry for Development_versions, associated text: Splitscreen functionality[2]
In-game help guide.
How to play/tutorial screen
New loading screens with tips
Redesigned crafting UI incorporating the recipe book
Options
World starting preferences
Starting Map
Bonus Chest
Trust Players
Game rule preferences
TNT Explodes
Natural Regeneration
Game rules can be toggled in the options menu
Player permissions
In-game server host options
Worlds can now be set to Invite Only, Friends Only, or Friends of Friends
Render Clouds and Fancy Leaves can now be toggled in Video Settings
Remix 3D export functionality (Windows 10 only)
Underwater particles