There are only a phew things that BB+ has that BBTUD doesn't. I can't really guess what this V3 will have.
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Grappling hook
Camping challenge (updated)
Faculty name tag
Portal poster
Grapple challenge
Soon to be : Dr.Reflex
An outside area with a working tree
A *SILENT* library
Whirlpools
Some events
And a few mechanics like the one way yellow door.
That's it. The chalk eraser is missing too but the potion thingy somewhat replaces it.