1. Introduction of the game
Grand Theft Auto III, developed by Rockstar Games, is a seminal title that brought the open-world genre into the 3D era with its release. Set in the fictional Liberty City, inspired by New York City, players navigate the game as a silent protagonist named Claude, who finds himself embroiled in a world of crime and betrayal after being left for dead during a bank robbery. Players explore three main islands, engaging in a wide range of criminal activities while pursuing vengeance and climbing the ranks of the underworld.

2. All characters and levels of the game
The game is populated by a cast of memorable characters, each with their own quirks and backgrounds, contributing to the game's gritty and immersive storyline. Key characters include Catalina, Claude's treacherous ex-girlfriend; Salvatore Leone, the head of the Leone crime family; and Maria Latore, Salvatore's troubled wife, alongside a myriad of other crime bosses, gangsters, and street-wise personalities that Claude interacts with across various missions. The game doesn't have distinct "levels" but is broken down into missions and quests that span across its three intricately detailed areas: Portland, Staunton Island, and Shoreside Vale.

3. What attracts users most to the game
Players are most attracted to the game's open-ended gameplay, allowing them to explore the vast city freely, commit crimes, evade the police, and engage in side activities such as driving taxis or putting out fires as a firefighter. The game’s immersive storyline and voice acting, dark humor, and culturally relevant soundtrack also greatly contribute to its allure.

4. Why it is popular
Grand Theft Auto III gained popularity due to its revolutionary 3D open-world gameplay, a significant leap forward in gaming technology at the time. Its mature themes, freedom of action, and narrative depth offered players an experience unlike any other game during its release, setting a new standard for video games as a form of entertainment and storytelling.

5. When the game was released and how many versions are currently available
Grand Theft Auto III was released on October 22, 2001. While there's only one version of the game, it has been ported to various platforms over the years, including PlayStation 2, PC, Xbox, mobile devices, and more recent consoles through digital re-releases. Additionally, a visually enhanced version was included in the Grand Theft Auto: The Trilogy – The Definitive Edition, released in 2021.

6. The most difficult part of the game
One of the most challenging aspects of Grand Theft Auto III is the notorious mission "The Exchange," which requires players to navigate a gauntlet of enemy fire with limited weaponry and health. Other difficult elements include the game's sometimes unforgiving wanted level system that can make evading law enforcement particularly challenging.

7. Strengths and weaknesses of the game
Strengths of Grand Theft Auto III include its groundbreaking open-world design, deep narrative, voice acting, and the impressive level of interactivity within Liberty City. However, the game also has its weaknesses, such as somewhat dated graphics by modern standards, a lack of an in-game map or GPS system for navigation, and occasionally clunky shooting mechanics.

8. What other games have been developed by the same developer
Rockstar Games, the developer of Grand Theft Auto III, is also known for developing other critically acclaimed titles such as the Red Dead Redemption series, the Max Payne series, Bully, L.A. Noire, and more recent entries in the Grand Theft Auto series, including Grand Theft Auto IV and Grand Theft Auto V.