COPR cannot be extended. I belevie the COPR is usually 1 year from the medical expiration date and maybe 6 months if they extended medicals. My original medicals was Oct 2020. I also did an upfront remedical which was updated in my portal. My upfront was in Feb 2022 and my COPR is until Feb 12 2023.
Also it's okay to travel to Canada even if H1-B is picked and start date is Oct. The only thing that differs will be you'll not automatically get ported (Change of Status denied) to H1-B in Oct. You'll remain in whatever visa status you are currently in until you leave the country and get stamped to begin your H1-B. I'd suggest you start looking at visa dates in Ottawa, right now they are available for March 2023. Once you get COPR activate it and return to US in your current visa status and when your H1-B comes through in OCT, you'll be told if your change of status has been granted or denied.
I myself have traveled while my H1-B application was in process back in 2018. My COS was denied, but another friend who also travelled got hers approved and directly ported to H1-B. So don't worry about H1-B and travel since PR to canada is a once in a lifetime opportunity that is worth it.