In the chapter 14, before heading to the Kingdom of Lucis, Noctis
finds himself in a world covered in darkness and overrun by high level daemons.
When I first came to this part of the story, I was not strong enough to fight these daemons and was forced to continue.
I have since beaten the main story and completed the post-game content in chapter 15 and my character's level has increased to a point where I have a chance against the daemons within chapter 14.
Is it possible to return to the Lucis where Chapter 14 takes place?
Best Answer
According to a post in this thread, no, you cannot return to future Lucis.
I believe that this save file is beyond a point of no return, which means you won't be able to leave the area and return to open world future Lucis.
That said, I haven't seen any evidence of there being sidequests in Chapter 14's future Lucis, though, so I don't think you're really missing anything.
Since there isn't a way to do so in NG, the only way for you to fully explore future Lucis would be to progress your NG+ file to that point. Since you retain levels, you won't have much need to grind in order to stand a chance against the high level daemons.