The flashbacks, which are showing us Olivers life during the five years he was supposedly dead, are there to develop his character further and show how he became the hero we see today, and also act as a mirror of sorts to the present-day plot. They havent always successfully managed this, but in season 3 the flashbacks, for the most part, didnt seem to serve any real purpose. Set in Hong Kong, it established his relationship as Maseo and Tatsu, and showed us the virus that would play a part in the season finale, but then just seemed to keep treading over the same ground each week without offering anything new. Season 4s flashbacks, wherever they take place Russia? Coast City? must ensure that they serve the character and the main plot, while being entertaining and forward-moving moments in their own right.