So I've landed and the immigration agent crossed my single entry immigration visa to cancel it. However, he didn't cancel my multiple entry unexpired worker visa. Does mean I could travel abroad without a PR card and airlines will let me to board a plane back to Canada based on this visa, then I could present my COPR at Canadian border to check to be let in ?
I think they will let you board with your work visa unless it has extremely short life.
You will be fine at the immigration gate just showing your passport (and CoPR just in case).
I have asked two different CBSA officers at two different locations what documents will be required for re-entry.
One says "passport is enough and keep your CoPR in a safe place", and the other officer says "bring both".