1. if your UG is cleared ex/ORD they will collect the cert there......

technically staff will then have to add "CERT PULLED" into the computer system for your ORD-YYZ-HKG flights. if they dont, then you will most likely be asked for a second cert at YYZ.

the best is to let the GA @ ORD know you have a connecting flight, so they would add it in asap and when arriving to YYZ, ask the conceriege to double check and show him/her your previous boarding pass (ORD-YYZ) that you have been upgraded using cert.

2. if your UG is not cleared in advance or at check-in, they will not collect your cert @ ORD regardless of upgrade or not and be on the Aerolotto program @ YYZ.