They'll find something else to worship. After all, even people who have no belief in a god still worship celebrities and politicians. Hell, politics is a religion for many people. I think religion was initially invented long ago for people to focus their worship needs onto. The majority of people feel a need to follow and look up to someone, religion fills that need.

Is it possible for humanity to believe in a “NO”? Somehow someone will turn the “NO” in to a new believe system, by claiming the devil or other similar character is tricking humanity.

Does this only aply TO humans
Are there any religious animals. Humans have existed for a quarter of a million years. I have fossils dating back to 400 million years. How does these creatures relate to a god. Dinosaurs existed for 65 million years, did they have a god

Society would flatly ignore it, sadly enough.

The Devout will deny the science.

I think crime and whatnot would increase, no fear of hell or other consequences.
I also think advances in science and healthcare would increase, through funding which would otherwise go elsewhere.

Then philosophy will unite people with the same effect. Nothing will change. Other than the moment you take the threat of an afterlife from some people, they will feel free to run amok. Some people need that check and balance. When someone asks 'how do you maintain morality without religion?' What they are implying is that they wouldn't maintain morality without religion. Scary proposition.