If divorce between a woman and a man has not taken place according to Sharī'ah (the man has given three divorces in one go), then what status will such a divorce hold?

As a principle, all cases of divorce which take place against the Sharī'ah must be brought before the court. It is up to the judge to give a ruling in them after hearing all the relevant details. Only he is the competent authority to decide the fates of cases which violate the Sharī'ah. There may be cases in which he imposes the divorce sentence and there may be others in which he does not do so and still others in which he gives some other ruling -- all depending upon the circumstances.