Thank you so much guys !! Your time and effort are really appreciated! ^
I checked the price on ITA software, the lowest price is about $2700, kinda out of my budget for a 3 or 4 days stop in Napal.
I don't mind buying a one way ticket to PVG, so the price would be lowered to about $1600, YYZ-EWR-DEL-KTM-LXA-CTU-PVG, leaving YYZ on Jan 8, and heading to PVG on Jan 12.
After a long holiday in PVG, I will buy a ticket around $900 for a round ticket.
I may go ask the travel agent see what they can offer me.