Skillsl needed for IOS game development

If you would like to create an iPhone game, you will need to finish the entire iOS Track (MINIMUM) You said you are on functions, which means you're still pretty knew to iOS Development as a whole. Also, The Objective-C for Swift Developers course is not a very long course, as it omits knowledge you already are familiar with in Swift. On top of that, Objective-C is still very useful and present to this day. Most Apps written in "Swift" still use many custom objects written in C / Objective-C. Therefore, it isn't 100% written in any one language. Objective-C will also help you understand the inner workings a bit more, since it is a lot less refined, and requires you to read in-between the lines to understand everything. So to answer all of your questions:

You need to have completed the iOS Track (If treehouse is your only source of knowledge) and done some personal research to be ready to develop games. Game Development (If the game you desire to create is 2d) is usually done with the various APIs apple has written, which means after learning Swift/Objective-C, you really just need to brush up on the APIs and put them to practice. Also, it is possible to create a game in ONLY Swift, but it is also quite cumbersome. I recommend learning both. In fact, thats what I'm doing :)