I want to know the exact process of standby for a flight. I am booked on a 1915 flight from YYZ to YVR and there are no J seats left for upgraade so i want to standby for the 1745 flight from YYZ. Even though Ihave travel a lot, I have never standby for a flight and with the Spill over from AC, flight are filling up quickly.
Couple questions:

1. If I am standing by, can I ask for an upgrade right from the beginning? What are
the success rate of that?

2. If I don't get upgraded on 1745, can I go back on the 1915 as a confirmed
passenger and again standby for an upgrade?

3. Usually, what are the success rate of being upgraded standing by for another
flight. I have 3 pax in my family including myself.

Thanks and let's hope AC doesn't go on strike causing us to lose all of R seats.

Regards,
Empress