Yes, you can keep exploring and engaging with various activities in Final Fantasy 7 Rebirth even after completing the main story. Here are the detailed steps and options available:

### Post-Game Activities

1. **Chapter Selection Menu**:
– After completing the main story, a prompt will appear to make a new save file of the completed run of the game.
– Load your completed save file and go to the **System** menu in the Pause screen. From there, you can access the **Chapter Selection** menu.
– You can replay any of the game’s 14 chapters with your current progress, including character levels, Materia levels, and affinity rankings between Cloud and his friends.

2. **Retain Current Quest Completion Data or Restore Previously Completed Quest Data**:
– When selecting a chapter to replay, you have the option to:
– **Retain Current Quest Completion Data**: This carries over your completed quest data from your current playthrough.
– **Restore Previously Completed Quest Data**: This imports progress from different save files, allowing you to restore previously completed quests.
– **Reset All Quest Data**: This resets all progress for the chapter, allowing you to complete quests again without affecting your completion status.

3. **Hard Mode and Additional Challenges**:
– You can play chapters on Hard difficulty, which is required for some trophies and provides additional challenges.
– Hard Mode mini-games and Combat Simulator missions offer ultimate completion challenges, including new Combat Missions centered around Zack and Sephiroth.

4. **Open-World Activities and Side Quests**:
– The game includes numerous open-world activities, side quests, and mini-games that can be replayed or completed after the main story.
– You can find new content, such as manuscripts and other items, while playing on Hard Mode.

5. **Play Log and Relationship Levels**:
– The **Play Log** section in the **System** menu displays your exact completion stats, including mini-games, Chocobo Stops, and Caches.
– You can also see your current relationship level with each character in your party, which can be influenced by dialogue choices and interactions.

6. **Extra Settings and Customization**:
– You can customize your companions for specific chapters, such as choosing who to accompany you during Chapters 8 and 12 at The Gold Saucer.
– Additionally, you can set the game to skip interludes involving Zack or adjust settings for Tactical Mode and material collection.

### Detailed Steps

1. **Complete the Main Story**:
– Finish the main storyline of Final Fantasy 7 Rebirth.

2. **Save Your Progress**:
– A prompt will appear to make a new save file of the completed run of the game.

3. **Access Chapter Selection Menu**:
– Load your completed save file and go to the **System** menu in the Pause screen.
– Navigate to **Chapter Selection**.

4. **Select a Chapter**:
– Choose any of the game’s 14 chapters to replay.
– Select one of the options:
– **Retain Current Quest Completion Data**.
– **Restore Previously Completed Quest Data**.
– **Reset All Quest Data**.

5. **Play on Hard Mode (Optional)**:
– If you want to play on Hard difficulty, select that option before starting the chapter. This cannot be changed once you begin playing.

6. **Explore Open-World Activities and Side Quests**:
– Engage in various open-world activities, side quests, and mini-games that are available after completing the main story.

7. **Check Play Log and Relationship Levels**:
– Visit the **Play Log** section in the **System** menu to see your completion stats and relationship levels with party members.

By following these steps, you can continue exploring and engaging with the game’s content even after finishing the main story of Final Fantasy 7 Rebirth.