Unfortunately, nope, it's not legal. The SIN-DXB segment is the one permitted crossing between IATA3 and IATA2.
(The rough line that seperates them runs south down the Ural Mountains, then between Iran & Turkmenistan, Afghanistan, Pakistan with IATA2 to the left of that line and IATA 3 to the right. It then basically runs straight down the 60 degree line to Antartica.)

Cheers.