Legal Question in Immigration Law in United States

I would strongly suggest you immediately sit down with a knowledgable immigration attorney to explore your options. There are way to many questions I have to properly answer the question you've posted, and ensure you get a good answer.

Assuming you mean your provisional waiver was denied and now you have an appointment for an immigrant visa interview at the consulate in your native country (not at the NVC)... If you attend that interview and they determine you are inadmissible, you will be denied a visa to the United States and will not be able to return. They will tell you that you have to apply for an inadmissibility waiver, which you can do from abroad, but just like your provisional waiver, it can be denied, especially if you're just resubmitting what you originally submitted in support of the provisional waiver. You can't appeal a provisional waiver denial, but you can reapply. Before you decide whether to leave the country to attend the interview and apply for a waiver from abroad (because that will be your only option at that point), you should schedule a consultation with an immigration attorney, and bring them a copy of everything you submitted to USCIS so they can tell you whether it's worth reapplying for a provisional waiver first (or to see if you have other forms of relief available). If you're in NJ, I can help you, and I don't charge for consultations.