I just did the YYZ-SIN route and returned last week. I flew YYZ-YVR-HKG-SIN, used eUpgrades to upgrade on YYZ-YVR (at the gate) and YVR-HKG (Upgrade confirmed 4 days before departure) 17 eUpgrades for that journey

As I reached my next threshold, I received another 10eUpgrades credits, which allowed me to upgrade on the return and again got HKG-YVR upgrade confirmed 4 days before departure and got by YVR-YYZ confirmed at the gate. I did have a 6 hr layover in YVR.

My HKG-SIN-HKG sectors were booked under SQ flight numbers in 'L' class I believe to get the 100% mileage accrual... Booked it through a travel agent....