Everyone has questions, it's okay. Here you might find what you were looking for.
Q1 - Why do I need a different account since I already have a CityU account?
A1: Simply because CityU official didn't approve API authentication for the site to integrate with CityU account. So this site only allows users with @cityu.edu or @cityuniversity.edu email to sign up.
Q2 - What are the differences between CityU Pics and Instagram?
A2: Fairly good question. The main and most important reason is that CityU Pics is for CityU accounts only which means that more control and more relevance it would provide for you to explore people's feed and trend.