Yes, my OP is "waiting for approval", may due to the 2-3 times update in short time.Thanks for the clarification. For some reason your initial post seems to have disappeared now.
In any case, your options in order of preference are:
1) Return to Canada by your latest return date (May 2020). This will guarantee you will not have any issues. The price for peace of mind will be an expensive airfare, as you say.
2) Return to Canada as soon as you can find a reasonably-priced flight. The lower your breach, the better the chances that you will not be reported. But the risk is always there, and it's tough to say how a PR in breach of RO (however small the breach may be) will be treated and questioned while travel restrictions are in place. One the one hand, CBSA may focus more on enforcing health-related issues and may have less capacity to deal with RO compliance. On the other hand, questioning at the primary inspection line may be more extensive than usual for the exact same reason, and this may make it more likely that your RO breach will be discovered. It's hard to say - we simply don't know. Nobody on this forum has reported any experience trying to enter Canada during lock-down while also being in breach of RO. It's a gamble.
3) Return to Canada when travel restrictions have been lifted and normal travel has resumed. This is the least preferred option and may be a big gamble.
Remember that one of the factors officials will look at is whether or not you returned to Canada at your first opportunity. While you might argue that returning to Canada on a $10k+ ticket is not feasible, it's unclear if officials will take the same view. Therefore, it is best to return as soon as possible.
As for your cough: since you have had your cough due to an existing condition, you should be able to board a plane. I am unsure how they check for your symptoms, but if it's not super-obvious (i.e. coughing literally multiple times per minute) I would think you should not have an issues.
Besides that, there must be some sort of medical record that outlines the condition that you have? How did you disclose it during the upfront medical you had to do for your PR application?
Thank you for your detail reply. You are right, maybe a "expensive" ticket, e.g. CAD8,000, is just in my mind but not in the CBSA officer's agree...this is possible. So, when I talked that I don't want to bring potential spread risk to community and don't want to bring burden to medical resource of Canada is more weak.
I do have hospital record papers in non-English, since year 1996....I will manage to find them out if I can......
I cannot remember there is somewhere in my PR application asked to declare about chronic cough, pharyngitis...
If it's saying the declaration in medical exam, I think I told the every truth of my health status, no one want to make misrepresentation, I also understood the chronic cough will not be a reason lead to a fail of medical exam, so I think I told the truth.
(if you have an idea about where to check the medical exam history, please kindly let me know)
I do health check every year, this is benefit from my employer too, X-rays to lung, blood test, etc, never have an issue about lung.
The chronic pharyngitis is common problem, not serious for me, but just will lead occasion cough, for example....1-2 times every 1-3 hours? But if the air condition not good, or smelled very hot/cold air, will make the cough more serious in short term, let's say 1-2 mins, just like takes some time to suite the air condition.
I think it will be better to check with CBSA about what kind of test result they will consider.
Thank you again.