**Introduction of the Game:**

"Rules of Survival" stands as an exhilarating battle royale shooter where players fight for survival on an expansive island laden with weapons, vehicles, and gear. In a fierce contest against up to 120 opponents, players parachute into the battlefield, scavenging for resources and engaging in intense combat, with the sole objective of being the last person standing.

**All Characters and Levels of the Game:**

The game offers a variety of characters that players can choose from, each with customizable outfits and accessories to stand out in the arena. As for the levels, "Rules of Survival" does not have structured levels per se, but rather features different game modes and a continuously shrinking play zone that forces players into closer quarters to intensify battles as the game progresses.

**What Attracts Users Most to the Game:**

Users are most captivated by the game's sprawling, dynamic environments, its compelling last-man-standing gameplay, and the adrenaline-rush-inducing combat situations. The freedom to develop unique survival strategies and the frequent updates with new in-game content also keep players highly engaged.

**Why It Is Popular:**

"Rules of Survival" gained popularity due to its high-octane action, accessible mobile gameplay, and the massive multiplayer experience it provides. It was one of the early mobile games to bring a fully-fledged battle royale experience to handheld devices, allowing players to partake in this popular genre on the go.

**The Most Difficult Part of the Game:**

One of the most challenging aspects of "Rules of Survival" is the final stage of the match, where the playing field is significantly reduced and combatants are forced into close proximity. Here, strategic play, quick reflexes, and efficient loot management become critical. Plus, outlasting other skilled players in this high-pressure scenario is a hard-won achievement.

**Strengths and Weaknesses of the Game:**

Strengths of "Rules of Survival" include its vast, open-world environments, variety of weapons and equipment, and the thrilling multiplayer gameplay. The weaknesses could be considered in terms of occasional performance issues, particularly on less powerful devices, and in some cases, the game might face balance issues or bugs that could temporarily detract from the player experience.

**What Other Games Have Been Developed by the Same Developer:**

"Rules of Survival" was developed by NetEase Games, a Chinese company known for many other successful titles such as "Knives Out," another battle royale game, "LifeAfter," a post-apocalyptic survival game, and "Identity V," an asymmetrical horror game, among others. NetEase Games is recognized for delivering a wide range of high-quality mobile gaming experiences.