Like mothman said, most virtual game console games are not in 3D. The ones that are are called 3D classics.
No you cannot play demos yet ( Unless you live in Japan, I believe). Demos are promised for all regions, but most of the world hasn't gotten them yet. And for the last question, I believe that promotion has only been confirmed for Europe. No word yet whether other regions will get it. I believe all of this info is accurate lol but you never know .
I am a nintendo fan, not a nintendo fanboy