First, ask your friend to mail you a T1 General 2001, after it is done, send it back to CCRA via your friend, don't forget to sign it at the botton of Page 4 of T1.
Second, file it as soon as you come back from China in May. I believe that you can continuously have CCTB in July 19, 2002. Don't worry about your Provincial Sales Tax Credit, you are not allowed to have Property Tax Credit.(If you live in Ontario like me, it is totally different.)