Meta Developer interview questions

So far have had 3 interviews and am going onsite for further interviews (I am an international candidate). First was a "general chat" lasting about an hour, including some basic technical questions about the Objective-C runtime. Second and third interviews were technical/coding challenges - an easier question and harder question. Coding is done in a shared online code editor. At every stage the recruitment contact has been *very* helpful, and the technical interviewers were also great to get along with.