1. Introduction of the Game:
MapleStory M is a free-to-play, side-scrolling MMORPG (Massively Multiplayer Online Role Playing Game) developed by Nexon. This mobile adaptation brings the beloved world and characters of the original PC game, MapleStory, to the palms of players around the globe. Offering a rich, fantasy experience with vibrant graphics, MapleStory M allows players to embark on epic quests, conquer challenging dungeons, and team up with friends to defeat powerful bosses.

2. All characters and Levels of the Game:
MapleStory M features a variety of characters that players can choose from, each with unique abilities, skills, and playstyles. These characters include classic MapleStory roles such as Dark Knight, Bow Master, Night Lord, Bishop, and Corsair. As players progress, they level up their characters by gaining experience through quests and combat. Higher levels unlock new abilities and allow players to venture into more challenging areas with tougher monsters and rewarding loot.

3. What Attracts Users Most to the Game:
Players are most attracted to MapleStory M for its nostalgic gameplay experience and its immersive, social community aspect. The game replicates the charming, pixelated art style of the original while incorporating modern enhancements. Its accessible mobile platform and engaging content updates foster a dedicated following who enjoy both solo adventures and cooperative gameplay with friends and guildmates.

4. Why It is Popular:
MapleStory M is popular because it successfully translates the appeal of the original MapleStory to mobile devices, making it accessible anytime, anywhere. Its easy-to-learn mechanics, combined with the depth of content and social features, have created a loyal fanbase. The continual updates, events, and generous free-to-play model also contribute to its sustained popularity.

5. When the Game Was Released and How Many Versions are Currently Available:
MapleStory M was released globally in July 2018. While the game itself is continuously updated with new content and events rather than distinct versions, it has seen numerous updates that have expanded the world, added new characters, and enhanced gameplay mechanics since its release.

6. The Most Difficult Part of the Game:
One of the most challenging aspects of MapleStory M is the endgame content, which includes high-level dungeons and boss raids that require strategic teamwork and powerful gear. Another difficult element is optimizing a character's potential through the game's complex system of equipment enhancement, requiring significant investment of time and resources.

7. Strengths and Weaknesses of the Game:
Strengths of MapleStory M include its charming art style, the depth of its gameplay, and strong community features. Weaknesses might include the potential for pay-to-win scenarios, as the use of in-game purchases can significantly speed up progression. The game's complexity may also present a steep learning curve for new players.

8. What Other Games Have Been Developed by the Same Developer:
Nexon, the developer of MapleStory M, is known for many other successful games, such as the original MapleStory on PC, KartRider Rush+, Vindictus, and Mabinogi. Nexon continues to be a major player in the free-to-play online gaming market, with a focus on both PC and mobile platforms.