I just want to ask, if after nikah, husband and wife had no sexual relationship and got divorced, does the husband still has to pay mahr to the wife?
Husband should still give the Mahr. But if no sexual relation took place, then the Mahr would be half. That means, if the actual mahr is 10 lac $, (former) husband should pay 5 lac $.
وإن طلقتموهن من قبل أن تمسوهن وقد فرضتم لهن فريضة فنصف ما فرضتم إلا أن يعفون أو يعفو الذي بيده عقدة النكاح وأن تعفوا أقرب للتقوى ولا تنسوا الفضل بينكم إن الله بما تعملون بصير
And if you divorce them before you have touched them and you have already specified for them an obligation, then [give] half of what you specified - unless they forego the right or the one in whose hand is the marriage contract foregoes it. And to forego it is nearer to righteousness. And do not forget graciousness between you. Indeed Allah, of whatever you do, is Seeing.