I booked RIC-HKG-XIY/PEK-IAD-YYZ for $384. This fare is only available between late October and early December. I did not find this fare for next year (RDU does have this fare, not RIC). Just use the google flight links provided above and click through all flights (United and Cathay Dragon flights). If you check on united.com, the low price may appear right away, depending how you do the multiple destination search. https://www.google.com/flights/?f=0#f=0&flt=RIC.HKG.2018-11-14.RICEWR0UA4426~EWRORD0UA426~ORDHKG0UA895*HKG.XIY .2018-11-16.HKGXIY0KA946*PEK.YUL.2018-11-19.PEKORD0UA850~ORDYUL0UA4400;c:USD;e:1;sd:1;t:f;t t:m;sp:.USD.40051*.USD.40051*.USD.40051 Note that it will save you $15 by searching/booking directly on united.com, instead of clicking the link from this google flight.
Regarding e-certificates, you cannot use them on this itinerary because there are partner flights. But USA-HKG/PEK-Canada open OJ may work.