Wow, thanks for all the quick responses! Definitely clears things up for me.

@adam.smith : Yes, it is a one-way ticket to Singapore with no stopovers/layovers in between.

I will be checking in online for all of the segments. I just want to make sure of all the technicalities so that I don't encounter any problems during the process. I guess I will need to exit YYC Domestic, and go straight to the UA booth then! I hope I have enough time!

Now since I already cleared US Customs in YYC, I would assume that I will not need to exit SFO to obtain my luggage and go through the process again for ANA? Or am I wrong?