Will have the same immigration questions as the US does. Don't foget the visa:
https://www.gov.br/mre/pt-br/consula...or-visa-e-visa
Yes, all international flights arrives at T3 and there is a shuttle between the T3 and T1 between 04:00 am until midnight every 15 minutes. You can pick up the shuttle in the 3rd lane in the arrival area.
The official GRU website is
https://www.gru.com.br/en