Sangeeta, thank you for a brilliant closing argument on this really trumped up issue!
Adultery is a legal issue if the marriage is valid. The marriage is not valid, so there is no adultery. This takes care of the audience POV.
Asad meeting Zoya or Ayaan locking Humeira in her room... From the audience POV, or the character POV is not iilegal, neither is it unethical.
The character POV... I think there is portrayal of a little confusion and denial here. The parties to the marriage know that they were not aware that they had said yes to the marriage. Zoya and Ayaan repeatedly told Asad that. Asad was on the verge of taking Zoya back ..he was just making sure to wait until there was no confusion. Then when Nikhat slit her wrist again, the nikaahnaama was signed.
After that Ayaan told Asad that he had no intention of honouring the document. So here, three characters out of four know that its not real. They don't know that its not legal, but they know that it can be proved invalid, or dissolved at worst. Thats the confusion part. Humeira is the only one who was not in the loop.
Sangeeta, I only differ from you in that I don't want Imraan to be redeemed, because then Najma will have to stay married to him! From the karmic perpective, the third OTP of the show should be Imveer 😃