No AI currently knows two techs. It is possible that one of them teched HBR instead of IW, but that would be surprising.
That's really weird.
The AI seem hardcoded to always tech Iron Working 1st if they don't have it.
I didn't think the window to liberate was that small.
I consider this one of the unsolved mysteries of Civ 4.
The threshold is fuzzy sometimes in my experience.
Sometimes 1 ruins the (Liberate), sometimes 3, sometimes it is 10.
Usually it is 1.
It gets really weird when Vassals sometimes accept a (Liberate) if it used to be their city even though vassals aren't supposed to be able to receive city gifts from a master.
(Liberate) always makes me sweat if it's not a city gift on the turn the city is founded.
This attached test game illustrates the immense problems with (Liberate)
Common knowledge says a new city can (Liberate) as long as it is closer to the AI capital than to any other capital.
So how come Shanghai near the Dye won't (Liberate)?
Spread religion to all (Liberate) cities and press next turn a few times.
Watch how a few cities lose the (Liberate) option, but others do not!
Even a barb getting too close to a city makes the (Liberate) option vanish.
The whole thing drives me crazy.