1. **Introduction of the game:**
FINAL FANTASY BRAVE EXVIUS is a mobile role-playing game that fuses classic FINAL FANTASY elements with modern mobile gameplay. Developed by A-lim for iOS and Android devices and published by Square Enix, the game features turn-based combat, deep character customization, and an original story set in the expansive realm of Lapis. Players embark on a grand adventure filled with memorable characters, dramatic battles, and strategic gameplay.

2. **All characters and levels of the game:**
The game boasts an extensive roster of characters (often referred to as "units") drawn not only from its unique universe but also featuring cameos from other FINAL FANTASY titles and various Square Enix franchises. Characters are categorized into different rarities and can be obtained through the game's gacha summoning system. Each character can be leveled up and enhanced to unlock new abilities and improve stats. Levels progress through a mix of story-driven quests, daily dungeons, vortex events, and trial challenges, each offering varying degrees of difficulty and rewards.

3. **What attracts users most to the game:**
Fans are attracted to FINAL FANTASY BRAVE EXVIUS for its rich story, nostalgic appeal of classic FINAL FANTASY characters, and the innovative blend of simplicity and complexity in its gameplay. The game's strategic depth, with its numerous abilities and equipment combinations, along with the regular introduction of new content and characters, keeps players engaged and consistently offers fresh challenges.

4. **Why it is popular:**
The popularity of FINAL FANTASY BRAVE EXVIUS can be attributed to its faithful reproduction of the FINAL FANTASY environment and the balance it strikes between accessible mobile gameplay and hardcore RPG elements. It also benefits from the strong brand recognition of the FINAL FANTASY series and the global community of fans looking to experience new stories and adventures within their beloved universe.

5. **When the game was released and how many versions are currently available:**
FINAL FANTASY BRAVE EXVIUS was initially released in Japan in October 2015, with its international release following in June 2016. As for versions, there is the original Japanese version and the global version, both of which receive regular updates and new content, although at different schedules and with some differences in available features and units.

6. **The most difficult part of the game:**
Arguably, the most challenging aspects of FINAL FANTASY BRAVE EXVIUS are the high-level trials and events. Trials often require players to have not only a strong team with high-level units and equipment but also to engage with complex strategies to defeat powerful bosses with unique mechanics.

7. **Strengths and weaknesses of the game:**
One of the game's strengths is its free-to-play model that allows a good degree of progression without monetary investment. It also has an engaging story, a vast array of characters, and a strong strategic element. On the downside, like many gacha-based games, it can become quite grind-heavy, and there is an element of pay-to-win for those who wish to consistently obtain the most powerful or rarest units.

8. **What other games have been developed by the same developer:**
A-lim, the developer behind FINAL FANTASY BRAVE EXVIUS, is also known for its work on the mobile game Brave Frontier. Both games share a similar art style and some gameplay elements. Brave Frontier is often cited as a precursor, having established many mechanics that were refined and adapted for FINAL FANTASY BRAVE EXVIUS.