Mytwocents, Xiaobaitu,or other experts, several more questions r

Hello,
one more quesiton regarding filling I-140. In my case, I am studying and living in US, and hold a Canadian Maple card.

So when I apply for US green card, in the sec 4 of I-140 form, if I write down "Canada" as my "last permanent residant country", do I have to provide photocopies of Maple card, landing paper, or both, together with I140 and I485?

Another question is, so in my case, do I need to provide the "non-criminal certification" from both China and Canada?

Question #3 is, do I need to provide photocopy of Canadian tax return form when I file the I-140 and I-485?

Many thanks in advance!