1. Introduction of the game:
"Snail Bob 2" is an engaging puzzle platformer that invites players to help Bob, the game's main gastropod protagonist, navigate through a series of diverse and inventive levels. This sequel to the original "Snail Bob" game enhances the adventure with new challenges and puzzles that require problem-solving skills and timely reactions to guide Bob to the exit of each level safely.

2. All characters and levels of the game:
The primary character in "Snail Bob 2" is, of course, Bob himself. Throughout his journey, he encounters various other characters, including his Grandpa, who often needs rescuing, and an array of friends and foes that add depth to the gameplay. The game features numerous levels—each designed with unique obstacles and mechanics that incrementally increase in difficulty to keep players engrossed.

3. What attracts users most to the game:
Users are most attracted to the game's charming graphics, intuitive gameplay, and the satisfaction of solving increasingly complex puzzles. Additionally, the whimsical character designs and the storyline add an emotional layer that many players find endearing.

4. Why it is popular:
"Snail Bob 2" is popular due to its easy-to-learn mechanics, which make it accessible to players of all ages, and the progressive challenge that keeps experienced gamers coming back. It strikes a balance between being a casual game that can be picked up for short sessions and a genuinely challenging experience for those seeking to master every level.

5. When the game was released and how many versions are currently available:
"Snail Bob 2" was released on September 24, 2015. As for the versions, the game has been updated and ported to various platforms, including web browsers, iOS, Android, and Steam, but is typically considered a single version with enhancements and additional platforms for access.

6. The most difficult part of the game:
The most difficult part of the game tends to be the later levels, where players must combine quick reflexes with strategic planning to overcome the multifaceted puzzles that often involve complex sequences of actions and precise timing.

7. Strengths and weaknesses of the game:
A key strength of "Snail Bob 2" is its well-thought-out level design, which keeps the gameplay fresh and engaging. Another is the game's overall charm, which is evident in the art style and character interactions. As for weaknesses, some players might find the pace of the game slower than typical platformers, and those looking for a more action-oriented experience may not find it as appealing.