1. Introduction of the Game:
Asphalt 9: Legends is a high-octane, visually stunning arcade racing game that puts players behind the wheel of some of the world’s most prestigious cars. Developed by Gameloft, this installment in the popular Asphalt series provides an adrenaline-pumping experience with improved mechanics, hyper-realistic graphics, and dynamic physics, offering one of the most immersive racing experiences on mobile platforms.

2. All Characters and Levels of the Game:
Unlike traditional racing games that may focus on characters, Asphalt 9: Legends is centered around its diverse range of cars, each with unique attributes and aesthetics, across various tiers and classes. As for levels, the game features a multitude of tracks set in locations around the world, each with different layouts to master and spectacular sights to behold. The Career mode in Asphalt 9 consists of several chapters, each comprising multiple series with races that challenge players to achieve their best.

3. What Attracts Users Most to the Game:
Players are most attracted to the realistic graphics, the thrill of unlocking and collecting prestigious cars, and the smooth, satisfying arcade handling that makes flipping and drifting through courses a thrilling experience. The inclusion of the "TouchDrive" control system allows even novices to quickly acclimate to the gameplay. Additionally, the multiplayer aspect and regular updates with new content keep the community active and engaged.

4. Why It Is Popular:
Asphalt 9: Legends is popular because it offers both accessibility and depth. The game's expansive roster of cars and tracks, coupled with its competitive multiplayer leagues and extensive single-player campaigns, offer longevity. Its ease of play and regular updates with fresh content also contribute to its popularity.

5. The Most Difficult Part of the Game:
For many players, the most challenging aspect of the game is competing in high-tier multiplayer races, where seasoned players with fully upgraded vehicles dominate. The skill required to perform perfect nitro boosts, drifts, and stunts while maintaining speed through various challenging tracks can be a significant hurdle for many.

6. Strengths and Weaknesses of the Game:
Strengths of Asphalt 9 include its stunning graphics, large selection of cars, engaging gameplay mechanics, and an active multiplayer community. As for weaknesses, some players might find the game's monetization and progression system to be restrictive, with a grind required to unlock the best vehicles without in-app purchases.

7. What Other Games Have Been Developed by the Same Developer:
Gameloft, the developer behind Asphalt 9: Legends, has created numerous successful mobile games. These include preceding titles in the Asphalt series such as Asphalt 8: Airborne, as well as other popular games like the Modern Combat series, Dungeon Hunter series, and the Gangstar series, which showcase the developer's expertise in crafting a variety of gaming experiences.