If I have to apply and pick up visa in person or can do that by a courrier?

You can send your application to CVASC by a courier and prepare a pre-paid return envelope of Canada Post Expresspost
The Center’s mailing address is 220 Laurier Avenue West,Suite 1450,Ottawa, Ontario, K1P 5Z9,Canada.
Anyway, you are suggested to visit website of CVASC for detailed procedure and fill the appliction form online.