Do I have to provide an itinerary in order to get a Brazil visa?
Yes. The Brazilian consulate will not issue a visa unless you provide proof that you are entering and leaving within 90 days. It does not need to be a purchased flight, but simply a reservation you have put on hold. They will also accept itineraries showing your entry and exit from South America (i.e. you do not have to show your are specifically entering Brazil) as long as the trip does not last longer than 90 days.