Use Facebook as a base as customers are more likely to use this than Instagram or Snapchat. Instagram would be more appropriate for the gallery as it is a a more visual platform. List events on Facebook so people can search by date.
I answered saying I would make sure areas were tidy and in order, put books away etc but this didn't seem like a sufficient answer for them as they were clearing waiting on me to expand. I still don't know what they were looking for in regards to this question.
I used to give these interviews for Herts Libraries. They are looking for the answer you gave, but you then need to expand with examples of you *demonstrating* this behaviour in your previous jobs or general experience. If you just give an answer and don't expand, you barely get a "point" and you definitely won't get the job. This is true for any answer to any given question in Herts Libraries. The flat answer, followed by example, and finalised with the effect of your example. For example: in my free time in my previous job, I did this and that, and this meant such and such happened more effectively, etc.