美国国内转身份后第三国签证的问题

1.You should apply F1 Visa, otherwise you F1 status will be invalid if you apply for F2 Visa.
2.You just get a stamp on your passport, that will ensure that you can come back to US if you travel overseas. It is neither status change nor renew of your visa.
3. I am not sure about the situation in Toronto, but I know that it is pretty easy at the Mexico border cities.