[Daynarr]

Ok here it goes:

1) When AI is building facilities it goes in order specified in that file, meaning he will first build the facility 1 if he can, then 2 and so on. The Last one (in this case 23) is usually used to fill up the unused spaces after all the other facilities are built (that's what 100 is for).

2) This option is used mostly by AI on large planets with lots of free space on them.

3) AI will build a facility if he has researched it. If that facility has system wide effect and he already has one in the system, he won't build another (e.g. he will build only one space port).

4) He simply upgrades them just like human player. Also, he does that as soon as he acquires necessary tech to upgrade.