Final Fantasy XV got the chapter selection option in the latest update. However, selecting a chapter will reset a lot of your progress: sidequests, hunts and hunter ranks, discovered parts of the maps, the works. You do get to keep your level, items and other character-related stuff. It also opens a new save file. Basically, it’s like NG+, and it allows you to farm powerful items.
FFXV Update 1.15 dropped recently, and, among other stuff, it introduced the chapter select option. It allows you to replay as many chapters as you want, and redo the stuff that you enjoyed doing. There is a bit of a catch, though.
As reddit user Asetoni137 pointed out, selecting a chapter will port over your characters, levels and items included. Story missions that you’ve completed up until the chapter you choose also remain untouched. On the other hand, it will reset all other progress that you’ve made up until the chapter that you’ve selected. This includes sidequests, hunts, tutorials; basically everything other than character progression. No worries, though: selecting a chapter will also create a new save file, so you won’t lose your progress unless you rewrite over the existing save.
Long story short: chapter selection is a kind of New Game +. What this in turn means is that you’re now able to replay select quests and hunts and get duplicates of items that you want. Of course, these duplicates won’t carry over to the original save, but just think of the possibilities. You can get duplicates of weapons, and arm both Noctis and the other appropriate character. You can have as many Adamantite Bangles and other items as you want. Essentially, all you have to do is replay Chapter 15 a few times, and your party will become gods among men. Pretty tempting stuff.