Let me start by saying that anything is possible with the PSO 20th anniversary coming up and all lore may be dropped to make a PSO Falz fight happen.
Beyond that let me see if I can address both questions from a lore perspective but I'll note this is spoiler heavy for Phantasy Star Portable 2 Infinity. Ragol is not really in an alternate timeline, but rather another universe separated by subspace. Time being relative, the events of PSO would have happened around the time that PSO2 Episode 2-3 would have happened on the JP side. Global is another thing as we're missing a certain sub-event from JP still. Suffice it to say, due to events elsewhere in the series, the events that took place immediately before PSO were effectively wiped from the timeline, preventing PSO from ever taking place. This all went down in Phantasy Star Portable 2 Infinity. During this game's post credit events you were able to team up with Red Ring Rico and fight Olga Flow preventing both Rico and Flowen's deaths. The missing sub-event is effectively a continuation of that involving one of the NPCs that journeyed with you to Ragol.
But let's suggest that original timeline continued on and that Dark Falz continued existing. Interviews suggest the Ruins were actually one of the Palmian Worldships that escaped after Garia crashed into the planet and that there was supposed to be a Lutz keeping this Dark Falz in check. Absent these events actually playing out in PSO, as well as the Coralian settlers not knowing anything of Algol, if anything a name related to the Amplum Umbra would likely be associated. That in mind, Dark Falz Germ would seem most appropriate, being applied retroactively after C.A.R.D technology had been developed.