Optimizations and bug fixing are a major part of game development; in fact, what makes one logic better than another is how bug free it is. What makes a game better for a player (regardless of the game design) is how fast the game runs. Now you have got your hands on the majority of the tools and techniques the pros use to find and fix their bugs, optimize their iOS game performance, and reduce the build size.

With all of that in mind, I would recommend that you go directly to the next chapter as you will be using this bug-free optimized game with its small installer file to submit it for review to the App Store.