So I ask you, just because 1000AD changed, does it means ALL of it changed?
No, not necessarily. However, the Yakra event was significant enough that people in 1000 AD remembered it. It was a major strike by the mystics against the Guardia royal family, and definitely not one of the mystics' finest hours if they were trying to garner sympathy from the player.
Heckran's dialogue is not related at all to the Cathedral incident, the only thing about 600AD that got changed.
Heckran doesn't mention it. If I don't say anything at all related to Jewish concentration camps, that doesn't mean it didn't happen. Again, it's starting to look like I need to repeat what I said before.
Heckran's dialogue is about the summoning. Nothing in the first trip on 600AD changed anything related to it.
Again, you're missing the point. You never get to see Heckran *before* tampering with 600 AD. For all we know, that could have played out very differently. THAT is my point.
...here, let me put it to you like this.
Let's pretend for a moment that Lucca's telepod sent Marle (and Crono, and later herself) to 2300 AD instead of 600 AD. Assuming everything plays out generally normal-like, Gaspar points them to Medina village so they can get home. They've never been in 600 AD before, nor has that period ever encountered them.
Normally, when you defeat Heckran, he would say "If only the Great Magus, who brought forth Lavos 400 years ago, had destroyed you humans..." In this alternate course of gameplay, he might have said something totally different: "If only Magus
had brought forth Lavos when he had the chance... !!!"
You guys have to understand I'm only claiming as a potential theory, not fact, that the Crono party's interference in 600 AD might have, via a chain reaction of events, caused Magus to get to work on that earlier, and that he originally may have never even started summoning Lavos to begin with. Whether or not Frog's self-esteem is involved is another story altogether.