In order to obtain Excalibur II in Final Fantasy IX, the player has to reach Gate to Space, a room in Memoria in under 12 hours of playtime.
That obviously means that several sidequests will have to be ignored, and some areas left unexplored, especially because some areas are inacessible after Disc 3.
However (excluding sidequests that can be done after getting the sword) what quests can actually be done, without compromising the ultimate goal (Excalibur II). Or in other words, what sidequests could be done during a Final Fantasy IX 12-hour speedrun playthrough?