1. Introduction of the game:
Embark on an epic adventure as you dive into the world of "The Seven Deadly Sins," a thrilling game inspired by the popular Japanese manga and anime series created by Nakaba Suzuki. The game masterfully weaves an intricate storyline, inviting players to join the renowned yet disbanded group of knights to clear their names and bring peace to the kingdom of Liones. Engage in visually stunning, high-resolution 3D battles, explore fascinating landscapes, and overcome trials with strategic depth that only the world of The Seven Deadly Sins can offer.

2. All characters and levels of the game:
Players are introduced to the beloved characters from the series, each with their unique abilities and backstories. You will assemble a team of characters such as Meliodas, Elizabeth, Hawk, Diane, Ban, King, Gowther, Merlin, and Escanor, going through multiple levels that reflect the anime’s storyline. The game's levels are intricately designed to challenge the player's combat skills, strategy, and team synergy, providing various scenarios ranging from dense forests to lively towns and eerie dungeons.

3. What attracts users most to the game:
The game's robust feature set includes real-time PvP battles, immersive storytelling, and crisp, console-quality graphics that immerse players in The Seven Deadly Sins universe. Engaging combat mechanisms, coupled with the ability to upgrade and customize characters, keep players hooked, while the faithful rendition of the series' humor and charm provides a sense of familiarity and delight for fans.

4. Why it is popular:
Its popularity is owed to its strong adherence to the original series' plot, providing a treasured sense of nostalgia for anime enthusiasts. Additionally, the tactical gameplay mechanics, accessible globally in multiple languages, attract a wide range of gamers who enjoy RPGs with a rich narrative.

5. When the game was released and how many versions are currently available:
"The Seven Deadly Sins" game made its initial debut in Japan, followed by a global release. Since its launch, there have been updates and new versions, each adding fresh content, characters, and events to ensure the gameplay remains exciting and current. As of my knowledge cutoff in 2023, it is advisable to check the game's official platforms for the latest release information.

6. The most difficult part of the game:
Some of the most challenging aspects of the game pertain to high-level PvP battles, where player strategy and character synergies are tested to the extreme. As players progress, they also encounter difficult boss fights that require a more in-depth understanding of character abilities and the strategic use of upgrades.

7. Strengths and weaknesses of the game:
The game's strengths lie in its engaging storyline, high-quality graphics, and character development system, which offers depth and replayability. However, its weaknesses could be seen in its potential for a pay-to-win model that limits free-to-play gamers and a grinding process that might be time-consuming for players who wish to progress without in-app purchases.

8. What other games have been developed by the same developer:
The developer behind "The Seven Deadly Sins" game, typically Netmarble, is known for several other popular mobile gaming titles. Notable games include "MARVEL Future Fight," "Lineage 2: Revolution," "King of Fighters ALLSTAR," and "Ni no Kuni: Cross Worlds." These titles showcase the developer's expertise in creating immersive RPGs with compelling storylines and engaging gameplay mechanics.