Here is answer for your question.

What are the next steps after receiving B# from Canadian Immigration?

-- You have to wait. They might ask for more document after IA.

Does B# guarantee that you are going to get landing certificate?

-- No, that is just your file no. Which you use to correspond or up date information.

How long does it take to get Canadian PR after receiving B#?

-- It depends where you apply. After you get approved ( Which will be after IA + they might ask for additional documents + medical & security clerence), they they will request your passport. It will take 6- 8 week after you enter in Canada.

Does everybody have to give interview here in USA places like Buffalo?
-- It might be waived or might not be. The interview can take place any where in Canadian visa offices(Buffalo – Detroit – Los Angeles – New York – Seattle – Washington, D.C.). You can choose when you apply it

Hopefully this will help.