Reviving Crono isn't a sidequest. Just because you can finish the BO after he dies dosen't mean anything. Reviving Crono is a part of the main quest, and everything after that is a sidequest... Except for the battle against Lavos, yes? Anyhow, you ought to think that bringing back Crono isn't so important... It's the process that matters. And a Time Egg really is something! And the Time Egg appears in Radical Dreamers, too. Being as you can finish Lavos through the BO without speaking to Gaspar, it means nothing, no?