Question

How to remove the movieclip by removeChild and later on clean the array for refresh purposes?

for (var t:int=0; t<8; t++) {
            circlesArray[2][t].removeChild(MovieClip)
        }

Answer 1

Ok so you have a circlesArray containing circle movieclips? Assuming the movieclips were added to the stage then:

for (var t:int=0;t<8;t++)
{
   removeChild(circlesArray[2][t]);
   //if they were added to some other movieclip then you would go
   //someOtherMovieClip.removeChild(circlesArray[2][t]);
}

If you want to clear the whole array then simply

circlesArray.length = 0;

This will clear the entire array but you may not want this since you seem to have other data in your multidimension array.