A:AnswerYes, it does cardstock fed through the back tray. Yes, it prints duplex (2-sided) and supports duplex copy/scan through the ADF. However, don't know if it will do both together, i.e. print on both sides of cardstock fed through the rear tray.
A:AnswerIt indicates it can print double sided. Too confirm, call Canon customer service and speaks to their Sales dept., they were very helpful explaining the functionality.