1. The dimensions extended backwards too, and a new timeline was "created" in which FATE had to monitor Home World too.
This might be the most plausible solution. The ghost scientist actually says something which seems to prove that, right before the lines that I quoted (I didn't notice it the first time):
An instruction to the young girl
in Arni 01 to give up going to
the main continent as a poet.
An instruction to the man in
Arni 02 to give up becoming
a fisherman.
A plan to avoid any point of
contact with the main continent,
so as not to affect history.
However...
Ever since the formation of
the Dead Sea 10 years ago...
(...)
There's Arni 01, and there's Arni 02. Apparently, Chronopolis did control Home World in the past, even though Home World is supposedly only created in 1,010 A.D. at the same time as the formation of the Dead Sea. It's interesting to note that while some ghosts do mention an incident with a "young boy", no one actually speak about a dimensional split. Perhaps FATE and the Chronopolis scientists are unaware of it and believe the 2 worlds always existed (which is sort of true if the split really extended backwards)?
In any case, to which worlds do "World 01" and 02 actually correspond to? On the one hand, the line about FATE not being able to intervene with World 01 suggests that 01 is Home World. On the other hand, there's a line about the girl in Arni 01 giving up going to Zenan to make a poet career, but it's only in Another World that we see that she gave up writing poems. In Home World, she still writes poetry and still wants to go to Zenan, though she's still hanging around in Arni for some reason.
...And here's yet another shot of crisis related to all these stuff:
[Man]
The Record of Fate tells
me not to go out to sea today.
That's why I'm here for
the chief's lecture.
Go against the Record
of Fate and you'll
regret it for sure.
Days like this, it's
best to take it easy!
We should all live
in harmony with fate.
[Man]
Hmmm....
The Record of Fate makes
no mention of me meeting
a demi-human...
No, no, you must
be mistaken.
The Record of Fate
never makes mistakes.
Those quotes are taken from Arni (Home). It's in Home World, yet the Records of Fate seem to still be working! How do we solve this?