1)Do i need a copy of my diplomas from the colleges in Canadian schools or should i also provide it from back home too ??
Copies of all diplomas/certificates after high school... from back home too.
And, just to make sure you are aware, CIC just released a revised set of application documents - instruction guide, document checklist, application form - so be sure you download the latest if you have not done so already.
http://www.cic.gc.ca/english/information/applications/cec.asp
The new document checklist changes the rules on transcripts - if you are qualifying as a temporary foreign worker, you only need copies of (all) transcripts. If you are qualifying as a post-graduate, you need to submit original transcripts. Since it does not state "from Canadian Universities" you have to assume they want ALL transcripts (from back home too).
2)Also, Isn't post-secondary school and college/university documents the same thing ???
Well, college and university are post-secondary, but post-secondary is more than that, it includes other types of education and training (any education after high school) that may not be "college" or "university", such as vocational training schools...