While knowing C certainly helps, it is not essential to learning Objective C, at least it wasn't for me. If you try first to understand it at a high level, then it is very doable (and fun!).
I don't think that the hamburger button was ever meant to look like a button. It's supposed to be a place that you can drag and move like a grip. The interaction where you can tap it and a menu will appear is just their for user convenience.
I've always felt that it would be only a matter of time before computer vision would be able to solve the (re)CAPTCHA problem. Especially since digit classifiers are able to match the performance of humans.
One approach that I enjoyed seeing was the use of reverse captchas. Here you pose a problem that a computer can easily solve, but a human cannot. For instance, if you ask a simple question (1+1=?), but you place the question box off the screen so the user can't see it. A computer would be able to easily answer the question, but a human user would have no way of doing so.