Core data layers  
 Sqlite vs core data 
 How to encrypt a core data database and Sqlite DB
 How will you handle a database corruption. 
 How will you initiate a post request?
 NSUrl connection delegates
 How to cancel an url request?
 How to make your server requests secure? 
 What are the design patterns you worked on? 
 Project management tools used ?
 Defect management tools used ?
 What is Agile ?
 Crash reporting tools used ?
 Encryption tools used ?
 oops concepts ? Abstraction, inheritance, encapsulation, polymorphism