I believe your friend will get served by his parents' attorney first. Of course, you may wait until then to consult with one himself.
2。我这位朋友有必要直接给对方律师写信说你的委托人所说不实马?
Don't do that with first consulting with a lawyer. First of all, everything he would put in the letter can be used against him later. Secondly the opposing attorney will believe in his clients rather than him. Finally the opposing attorney very likely will not respond to your letter at all due to some ethical issues.