Q. Can I have a playground without having to create a full Xcode project?
A. Absolutely. Xcode treats playgrounds as interpretable files, independent of any project.
Q. I am still running OS X Mountain Lion, can I still use Xcode?
A. OS X Mountain Lion (v. 10.8) can run Xcode, but the latest version of Xcode that can run on Mountain Lion is Xcode 5.x.
Q. I just started learning iOS development in Objective-C, but now Apple announced the Swift programming language. Should I still learn Objective-C?
A. Objective-C is still heavily used in many Mac and iOS apps and will still be used for some time to come. This book predominantly teaches the Swift programming language, but if you want to be a developer full-time or in some sort of capacity, you may encounter Objective-C code from an existing code base, so you may benefit from learning some Objective-C. A great introduction to iOS programming in Objective-C is John Ray’s book Sams Teach Yourself iOS Application Development in 24 Hours from Sams Publishing.