1. **Introduction of the game**
Teamfight Tactics is a strategic auto-battler game developed and published by Riot Games. As a spin-off from the immensely popular League of Legends, TFT shares many thematic elements and characters known as champions. Players compete against seven others in a series of matches to build the most powerful team by buying, arranging, and upgrading champions. Through combining champions with shared origins and classes, players craft synergies and strategies in a dynamic and constantly evolving battle for supremacy.

2. **All characters and levels of the game**
TFT features a broad roster of champions, each representing characters from the League of Legends universe. Champions are divided into tiers, often referred to as levels, that reflect their cost and power level, ranging from one to five. Players must make strategic decisions in champion selection, looking to balance their gold and synergies across low and high-cost units to optimize their team compositions. Additionally, champions can be upgraded by collecting multiple copies, increasing their strength significantly.

3. **What attracts users most to the game**
Players are drawn to TFT for its deep strategic gameplay that combines decision-making with luck and adaptability. The satisfaction of building a potent team composition and the excitement of a nail-biting match is a big draw. The randomness of the item and champion drafts also adds a layer of unpredictability that keeps the game fresh and engaging. Additionally, the frequent updates and new content released by Riot Games, including new champions, items, and themed sets, keep the community engaged.

4. **Why it is popular**
TFT's popularity can be attributed to its affiliation with League of Legends, its immersive gameplay, and its free-to-play model. The competitive aspect of the game, along with its ranked system, provides an everlasting quest for improvement and status within the community. Its accessibility across multiple platforms allows a wide range of players to enjoy the game.

5. **When the game was released and how many versions are currently available**
Teamfight Tactics was officially released on June 26, 2019. Since then, the game has maintained interest through the introduction of multiple sets or versions, each bringing unique themes, champions, and items, effectively serving as major updates or seasons. As of my knowledge cutoff in 2023, there have been several sets released, each refreshing the game's meta and ensuring a novel experience for players.

6. **The most difficult part of the game**
The most challenging aspect of TFT is adapting to the ever-changing game state. Players must pivot their strategies based on the champions and items they are offered and the compositions of their competitors. Mastery of the game not only requires knowledge of the current set's specific mechanics but also quick decision-making and the ability to anticipate and counter opponents' moves.

7. **Strengths and weaknesses of the game**
TFT's strengths include its deep strategic layers, the diversity of champions and synergies per set, and the involvement of a strong competitive scene. However, weaknesses could be seen in its dependency on RNG factors which can sometimes lead to an uneven playing field and can frustrate players aiming for consistency in their results. Additionally, the learning curve can be steep, especially when keeping up with new sets and balance updates.

8. **What other games have been developed by the same developer**
Riot Games, the developer of Teamfight Tactics, is widely known for their flagship title League of Legends. Apart from these, they have also developed other games such as Valorant, a tactical first-person shooter, Legends of Runeterra, a digital collectible card game, and have expanded into mobile gaming with Wild Rift. Moreover, Riot is also involved in publishing games, which includes supporting third-party developers under their Riot Forge initiative.