How to start iOS programming in 2013? [closed]

I just finished reading Apple's official guide Programming with Objective-C. Then I try to find some other books to continue learning. Sadly, almost all the books are out of date... So what's next?

Is it possible to develop iOS in Linux?

Being an iOS developer, you know that using Xcode (IDE), you will be able to develop iOS mobile apps. However, Xcode only runs on a Mac computer. Thus, you need different ways to develop iOS applications on Linux. For developing an iOS app on Linux, you need virtualization software.

How do I enable developers iOS?

As indicated by the alert, to enable Developer Mode go to Settings > Privacy & Security on the iOS device. Scroll down to the Developer Mode list item and navigate into it. To toggle Developer mode, use the “Developer Mode” switch. Tap the switch to enable Developer Mode.

I would highly advise taking the CS193P Stanford Course. About 5 months ago, I went through the whole thing. I just got down the very last concept of the course 5 minutes ago (lol). And I feel like I very thoroughly understand programming for both iOS and iPad.