For the first question, you can just fill in the approximate time, for example, if the I-20 shows the school will open at 08/20/2008, then you can just write 08/05/2008 to be the time you will go to USA. For the second question, I suggest you to write one and 1/2 year, that's just your estimate about the study life. 36 months problem has been asked a lot of times, let's answer it again, haha, VO knows that the school will write a little long to ensure your study, probably something happened (weather, schedule, etc.), then you can type the email from the university or type the true schedule (as you say, one year) to show to the VO (if he ask). For the last question, I have no idea, sorry, hope other friends to answer.
I am sorry this time I use English. Because there is no Chinese type method in the university computer in this lab.