REBIRTH uses EOS for cross-platform cloud saves and the "Pawn" minigame leaderboards. A FLT crack usually strips these out or provides a fake emulator. If the crack doesn't properly emulate EOS, specific side quests may hard-lock the game.
The original story of Final Fantasy VII, with its complex themes of environmentalism, corporate greed, and personal identity, is expected to be preserved, possibly with some enhancements or additional backstory. The deep and diverse cast of characters, from Cloud Strife to Sephiroth, will likely see a reimagining that could provide new insights into their motivations and personalities. Tag- FINAL FANTASY VII REBIRTH-FLT