Questions about uniques techs.

[Q]

If you give new unique tech areas numbers above 4 are the used??
I made two new areas and could not "find" them until I switched the unique number with two old unique technologies. But then these old technologies were not found any more. Of course this could be just coincidence.
What happens if you give two unique technologies the same number? Will you find two technologies at the same time?
Is there any possibility to modify the frequency of ruins except the map editor?

Any answers are greatly appreciated.