I have a DONE4 that was issued and travel commenced last year as follows: CAI-DOH-SYD-LAX-LHR-CAI.
1). Anyone speculate why that would have been issued as a DONE4 and not a DONE3? My orig routing is a EU/ME-SWP-NA-EU/ME.
2). Would I be able to maintain DONE4 by changing to the following: CAI-DOH-SYD-LAX-LHR-xJNB-DOH-CAI
3). Or, CAI-DOH-SYD-LAX-GRU-LHR-DOH-CAI?
3a). Assume that I couldn't modify 3) to instead be ...-GRU-xJFK-LHR-DOH-CAI?

Thanks