If your COPR says it is only valid until 2021/03/30, it is no longer valid.
If you still wish to travel and land, you will need to contact IRCC. They may or may not require additional medical examination, etc. Note that IRCC has been making arrangements to 'extend' (despite the language that says the date is final) due to covid - but they may not actually do so while the covid restrictions are in place, unless you qualify for an exemption under the covid travel restrictions (such as spouse living in Canada).
BUT: the issue is who can travel to Canada and land, even with a COPR. The COPR itself is not an exemption from the covid travel restrictions.
I don't know what they're doing for those who do not qualify under any of the travel exemptions - you had best post in and ask the question in the relevant forum for the program under which you were accepted as a PR-candidate (eg express entry or other). My understanding is that right now the answer is mostly "you wait."
I'm thoroughly confused by the various dates you've written though, so perhaps I've missed something.