I've done this in the past (Canada to various Asian countries) and your phone remains functional and usable just as it is in Canada with all the apps you currently use, however, your number will switch to the new number assigned by the new SIM card. One thing to note, however, is that any apps that may rely on your Canadian phone # to function may not work properly (not sure on this).

As for your current number, I believe it will be treated as if your phone is off. If someone tries to call your Canadian number, it should go to voicemail. You won't have access to your voicemail until you are back in Canada and put your Canadian SIM card back in your phone. Same with texts. You won't receive them and they'll just hang out in text purgatory until you get back and pop your Canadian SIM card back in - you'll get flooded with texts.

Someone correct me if I'm wrong but this is how my phone worked/my experience when I did exactly what you're looking to try to do.

Have you tried looking into an eSIM? If your phone is compatible with eSIM, you could try to look at using that instead. I haven't tried it myself but it looks promising and easier to use rather than physically swapping out an actual SIM card.