Few questions

[A-Man]

1- What Freaky has said. Can't be changed with AI scripting.
2- First, you loop on all the objects on the screen to see if they exist in the first place. And then keep incrementing some variable to "count" the valid opponents on the field. To do this, you do:

Code:

int no_of_opponentsonscreen=0;
bool rangecheckcondition=true; //you set your range conditioning here
for (int i = 0; i < 400; ++i){
    if (loadTarget(i) == 0 && target.team != self.team && rangecheckcondition){
        no_of_opponentsonscreen++;
    }
}
if (no_of_opponentsonscreen > 1)
    A();  //or whatever combination you would like to use.

3-Try messing around with "D()" parameters. I believe either "D(1, 0)" or "D(1, 1)" makes your character tap the defending key. Also, try placing a "D(0, 0)" after your "D()" as this will insure that D is continuously being pressed and released and not held.

4-Just use the Load target stuff to loop on all the targets, and then check if any is in your Z range moving with a velocity towards you. If true: Defend.