“If” your claim was rejected, that means they don’t feel you are a genuine refugee and the would send you back to your country of origin. That’s just how it works.
As explained, you can claim at the airport when you arrive. Whether your claim as a refugee is accepted, it’s impossible to say.
Your biggest issue will be obtaining a TRV to travel to Canada. As you are already a refugee claimant and residing outside of your country of origin, it is unlikely IRCC will issue you a TRV to travel to Canada.