Heres some news from Nesworld concerning 3DS Demos:

Anyway 2017 is almost over, so why not end the year with a few updates and the first one is a long overdue update to the 3DS demo "NFR" section. It has now been updated with all, to mw, known demo carts available in all regions and as something new there are placeholder pictures for those that has yet to receive a proper scan.
Anyway if you're interested then why not click on the link below