Pergunta de entrevista da empresa IDrive

1)All memory management related questions(Retain , release , copy) 2)Multi threading(dispatch queues, nsoperation queues) 3)Very simple data structure questions(Reverse a string ) 4) Can you alter the navigation stack? 5) How to stop background thread? 6) valueForKey or objectForKey? Why 7) Hierarchy of UIView 8) What is main and global queue? 9) WAP for serial and concurrent queues?