1. Introduction of the game:
Bloons TD 5 is a captivating tower defense game developed by Ninja Kiwi that invites players to embark on a colorful and strategic endeavor to prevent an onslaught of balloons, known as "bloons," from traversing through a set path on a map. The game challenges players to utilize a variety of towers and special agents, each with distinctive abilities, to pop the bloons before they can complete their journey.

2. All characters and levels of the game:
The primary characters in Bloons TD 5 are the towers and special agents. Towers range from the simple Dart Monkey to the powerful Super Monkey, each with upgrade paths that diversify their capabilities. Special agents are additional characters that can be deployed to provide extra support. The game features an expansive number of levels, categorized into beginner, intermediate, advanced, and expert difficulties, providing varied and incrementally challenging experiences.

3. What attracts users most to the game:
Players are most often drawn to Bloons TD 5 due to its engaging gameplay, the variety of towers and upgrades, and the game's replayability factor. With each level presenting a different layout and set of challenges, coupled with daily quests and special missions, there is always a new objective to strive for.

4. Why it is popular:
The popularity of Bloons TD 5 can be credited to its intuitive and absorbing gameplay, charming graphics, and a strong sense of progression and accomplishment. The game's ability to balance strategy and casual fun allows it to appeal to a broad audience, from casual gamers to those seeking a more in-depth tower defense experience.

5. When the game was released and how many versions are currently available:
Bloons TD 5 was released on November 15, 2012, and has since been made available across multiple platforms, including mobile devices, PC, and consoles. Various updates and versions have been launched over the years, incorporating new features and content to continually refresh the player experience.

6. The most difficult part of the game:
Many players find the expert levels and special challenges to be the most difficult parts of Bloons TD 5. These levels require meticulous planning, quick reflexes, and an optimal combination of towers and upgrades to achieve victory.

7. Strengths and weaknesses of the game:
One of the game's strengths lies in its simplicity coupled with depth; it's easy to pick up but offers deep strategic elements for those who wish to master it. On the downside, some players may find the later stages to be somewhat repetitive or that the game leans towards a "pay-to-win" model due to in-app purchases providing significant advantages.

8. What other games have been developed by the same developer:
Ninja Kiwi, the developer of Bloons TD 5, has also created other popular titles in the Bloons series, such as Bloons TD 6, Bloons Adventure Time TD, and Bloons Monkey City. Additionally, they have developed various other games outside the Bloons universe, including SAS: Zombie Assault, Fortress Destroyer, and Battle Panic.