How can I edit AI properties for Civilization 3?
Is it possible on scenarios level only or for whole game?
Well, you can't really edit the AI itself -- those routines are contained within the game-executables (Civilization3.exe, Civ3X.exe, and Civ3Conquests.exe) -- but you can certainly edit the 'ruleset' files for each version of the game (.bic, .bix or .biq, respectively), which
can improve the way the AI plays the game/ deploys its units.
All you need to do is open the Editor for the version of the game which you want to alter, and tell it you want to create a 'rules-only' .biq (which can be used to play on randomly-generated maps). You can also create 'map-only' .biqs (which will use the epic-game rules), or a 'rules+map' .biq (= a full mod, or scenario). You should be able to find all 3 versions of the Editor installed in the same place as the rest of your Civ3 gamefiles:
.../Civ3/Civ3Edit.exe (for Vanilla)
.../Civ3/civ3PTW/Civ3XEdit.exe (for PtW)
.../Civ3/Conquests/Civ3ConquestsEdit.exe (for Conquests)
And a few caveats: Editing the base-ruleset for the epic game(s) will prevent you from recording any scores for games using those rulesets. It will also exclude you from playing GotMs or submitting to the CFC HoF. Most modders rather create their own modified rulesets from the original files, and leave those in place. Modifying the ruleset-files can
also totally screw things up, so be careful, and make backups of the originals before you start messing around with them! If you fail to make backups, and something goes badly wrong with your mod, you may be forced to reinstall the game in order to be able to play it again.
For (a lot) more information and expertise, you should visit the
'Creation & Customisation' section of CFC
In particular I'm interested how to forbid AI destroying cities.
For this, you'll need a 'No-raze' patch for the relevant game-executable. The Conquests1.22-version can be downloaded from
this page on CFC. While many CFCers use this patch without problems, bear in mind that it is not an official, Firaxis-supported patchfile, i.e. you use it entirely at your own risk.