[akots]

@Stapel:

First level techs in Hellenistic age are not tradeable but subsequent techs can be traded once AI knows the first level techs. But you can get them all from the Great Library (or you can steal them). This is to limit exploitation of scientific AIs by a human player apparently.

Unit upgrades can be done in a city with Barracks which are only in your capital prior to Standing Military tech late in the Imperial Age. Also, there are a few resource requirements and these resources have to be hooked up as well.

And Monarchy is indeed Xenophobic.

Regarding flips: Are you sure there is no overlap with AI? You borders don't have to expand to have an overlap. If the 21 city tiles of your city overlap even a single tile with 21 tiles of the AI city, your city can flip.