I would think an undergraduate degree is useful in terms of salary. It is definitely an entirely different experience once you're in the classroom. You really can't prepare enough for it. You'll never really know until you have your own class. I went to a job fair at McGill and was recruited because French was one of my teachables.
Many individuals contact the school boards to see the openings available.
A No, but again it is recommended that you get to know the principals, staff at schools by volunteering, supply teaching. Warm contacts really help. A A teaching resume should be as thorough as possible. A See previous question. Again make it as thorough as possible.