My alliance member is at lev 14 and still doesn't have the exploring option.. how does he get this?

The answer is simple, you couldn't have had the option at level 12 because you need the fourth free builder make sure your alliance member has that built than it should work.

Not sure about this. The game does state that you can explore once you reach level 12. Perhaps there is another requirement to be met also.

It may also be worth your friend checking if his game needs an update in case there is a glitch. Or report the issue to the game support.