Due error, error: cannot declare variable 'Wire' to be of abstract type 'TwoWire' extern TwoWire Wire;

Official Hardware Mega Due
2

Hi, I would say that you just experienced a bug of the Arduino Due board library.
I suspect that you are currently using the version 1.6.12 of it.
Just usee the 1.6.11 instead and it will do the job
Best regards