i suggest you to apply from Vancouver if you are moving there like you said, because if you apply from Montreal than they will transfer your file to Vancouver local office and maybe it will take longer in process , so gather all documents from Montreal as proof like rent bail , bills, t4 , school record or university taxes etc.... also apply for your CBSA record if your travels from Canada and try to keep your current passport and the stamps on it , that's will be proof for them and for you , also if you want call CIC and they will tell you what you should to be sure best luck.