1. Introduction of the game:
Terraria is an action-adventure sandbox game that transports players to a vibrant and imaginative 2D world. With its unique combination of exploration, crafting, and combat, Terraria offers players endless possibilities to build, fight, and discover within its pixelated landscapes.

2. All characters and levels of the game:
In Terraria, players can choose from a variety of characters, each with their own unique abilities and play styles. Whether it's the versatile and agile Ranger, the powerful and melee-focused Warrior, the mystical and spell-casting Mage, or the resourceful and strategic Summoner, there is a character suited for every type of gameplay preference.

As for levels, Terraria is procedurally generated, meaning that each player's world is unique and randomly generated with different biomes, underground caverns, and treasures to uncover. From lush forests to desolate deserts, treacherous dungeons to soaring floating islands, players can explore countless levels in their quest for adventure.

3. What attracts users most to the game:
The vast exploration aspect of Terraria is one of its biggest attractions. The game encourages players to venture into the unknown, uncover hidden secrets, and engage in thrilling battles against a myriad of monsters and bosses. Additionally, the intricate crafting system allows players to build and customize their own unique structures and equipment, fostering a strong sense of creativity and personalization.

4. Why it is popular:
Terraria's popularity can be attributed to its addictive gameplay and its constant updates and content additions. The game's developers have consistently listened to player feedback and introduced new features, items, and challenges, ensuring that there is always something fresh and exciting for both new and experienced players.

5. When the game was released and how many versions are currently available:
Terraria was initially released on May 16, 2011, and has since gained a massive following. As of now, there have been multiple versions released, with the latest being Terraria: Journey's End, which was launched on May 16, 2020, to commemorate the game's ninth anniversary.

6. The most difficult part of the game:
The most challenging aspect of Terraria lies in its expert mode and the challenging bosses that players encounter throughout their journey. These bosses require strategy, quick reflexes, and a well-equipped character to defeat. Additionally, exploring the game's treacherous underground caverns can also pose a significant challenge as players face deadly enemies, complex traps, and intricate puzzles.

7. Strengths and weaknesses of the game:
Terraria's strengths lie in its expansive gameplay mechanics, its vast and diverse world, and its strong emphasis on exploration and creativity. The freedom to build and customize structures, the satisfying combat, and the constant updates all contribute to the game's appeal. However, some players may find the game's initial learning curve challenging, and the lack of a clear progression path might be overwhelming for newcomers.

8. What other games have been developed by the same developer:
The developer of Terraria, Re-Logic, has not only created this beloved game but has also released other notable titles. One of their prominent creations is Pixel Piracy, a sandbox pirate simulation game that offers players the chance to become a fearsome captain and conquer the open seas. Another popular game developed by Re-Logic is Pixel Privateers, a multiplayer sci-fi squad-based tactical RPG that explores the depths of an uncharted galaxy. These games demonstrate the developer's versatility and dedication to creating immersive and unique gaming experiences.