I'm quite sure you're expected to create an app from scratch. If you're familiar enough with making an app (as it seems that you are) then I would try your bes

I'm quite sure you're expected to create an app from scratch. If you're familiar enough with making an app (as it seems that you are) then I would try your best to make a new app as the idea is to present an application that is about you — think of it as an 'app resumé'; done as creatively as possible, of course! Last year, I made my app while studying for university finals that started a week after the submission deadline — it's not implausible ;)