FF7 Remake will be episodic...

[Dark Jaguar]

In the original game, most game regions and their data were stored on all 3 discs. This meant you could backtrack pretty much to any point. The exceptions were large sections of Midgar (which can only be accessed during the first section of the game) and the Gold Saucer (which is "closed for repairs" during disc 2). Aside from that, most of the space across the 3 discs is taken up by FMVs.

I must confess I did always want to see far more of Midgar than we were shown in the game proper.