Joe36
The airline of the first flight is usally the issuing carrier if done on line. Unless you can get another carrier to issue eg. AA via MindPearl

A flight AAA-BBB-CCC on 1 flight number is considered as AAA-CCC (1 segment) provided its an airport only transit You cannot stop over for a day or 2. If you do stop over its another segment

There is no guarantee that a A, D or L (*ONE*) seat wil be available when you want it. At the FIFA WC 2014 dates it will be hard to get any seat at GIG. Airlines only have reservations 355 day / 330 days out (depends on the airline)