As Shopify support said, all my questions is related with Shopify Payments, that is not available in Brazil, where is my Default market, assigned by my IP address... 

Hello! I created a store and want to sell all over the world.The default market was selected as Brazil.I also added Internacional and Oceania, totaling 3 markets.  I would like to:change the primary market, from Brazil to International;change Brazil'...