Effectively, the exercise prompt states "in the presence of the assumption that IQ scoring process follows a normal distribution, answer this question..." So you're allowed to assume that all of the properties of the normal distribution hold for the process generating the sample data: the distribution is symmetric, the distribution function characterizes IQ scores, IQ scores may be any real number, and so on. Obviously some of these are impossible (for example, since, to my knowledge, IQ scores must fall in some finite interval), but you're still permitted to assume them for the purposes of the question.
For the purposes of the question, at no point do the data become normally distributed. The data-generating process simply is a normal distribution by virtue of the question prompt.
Also there is a curve associated to the Normal Distribution, what does this curve tell, what stands on the axis?
These questions are already answered elsewhere on this website. This answer might be particularly helpful.