1. Is easy to test, units get owned by city that is closes to deconstructed city.
2. IIRC game does not protest to war declaration and nothing happens for the time being. But you'll break alliance and go to war with attacking player when he makes offensive move, as by definition he attacked your ally (if my first statement is not correct expect to break alliance with player declaring war).
3. If you mean work tiles on most rulesets it is constant (the one I'm working on it won't have it constant though, also that can be easily added to any ruleset), Civ 3 did not grow that area IIRC, and I played quite a bit of it. If however you talk about borders, Civ3 had them grow by culture (borders also provided vision; freeciv has option for that too). On freeciv it is ruleset dependent, borders can also be turned off altogether. On default ruleset borders do not expand IIRC, but start with ridiculous radius of 7... civ2civ3 has more reasonable approach, borders depend on city size (at least up to certain level).