1. Introduction of the game:
Yu-Gi-Oh! Duel Links is a digital card game based on the popular Yu-Gi-Oh! trading card game and anime series. Developed and published by Konami, it enables players to duel against each other using a variety of cards in a virtual environment. The game simulates the exhilarating card battles that fans have come to love from the original series but now they can on-the-go with a mobile or PC platform. It brings the competitive world of Yu-Gi-Oh! to life with vivid graphics and an interactive user interface.

2. All characters and levels of the game:
Duel Links features a range of characters from the Yu-Gi-Oh! universe, each with unique decks and special abilities known as "Skills". Players can choose to play as fan favorites like Yugi Muto, Seto Kaiba, Joey Wheeler, and many more, spanning multiple generations of the Yu-Gi-Oh! series. On top of character levels, players progress through stages (game levels) by completing specific missions. As players move up stages, they unlock new features and tougher opponents.

3. What attracts users most to the game:
Players are attracted to Yu-Gi-Oh! Duel Links for its faithful recreation of the classic dueling experience combined with quick-paced, mobile-friendly gameplay. The game supports a variety of deck-building strategies, a competitive PvP arena, and regular events that keep the gameplay fresh and engaging. The ability to collect and duel with cards from a vast pool, including iconic monsters and spells, as well as the nostalgia factor, are significant draws for fans.

4. Why it is popular:
Yu-Gi-Oh! Duel Links is popular because it offers an authentic experience for Yu-Gi-Oh! enthusiasts, which is accessible anytime, anywhere. The game's free-to-play model with optional in-game purchases allows a broad audience to enjoy the game at no initial cost. Moreover, its cross-platform playability between mobile and PC users, frequent updates, and in-game events contribute to its vibrant, active community and sustained popularity.

5. When the game was released and how many versions are currently available:
Yu-Gi-Oh! Duel Links was released on November 17, 2016, in Japan, and January 11, 2017, worldwide.

6. The most difficult part of the game:
The most challenging aspect of Yu-Gi-Oh! Duel Links can vary from player to player, but often it includes climbing the ranks in competitive PvP, understanding and countering the ever-changing meta, and obtaining specific cards to construct a powerful deck. Players may also find it difficult to keep up with the constant introduction of new cards and mechanics, which can change the strategic landscape of the game.

7. Strengths and weaknesses of the game:
The strengths of Yu-Gi-Oh! Duel Links lie in its engaging strategic gameplay, strong community engagement, and regular content updates. Additionally, the game's appeal to both nostalgic fans of the original series and newcomers to the card game is a significant strong point. However, its weaknesses could be seen in the RNG (random number generator) aspect of card acquisition, potentially leading to an imbalance if players do not wish to spend money on card packs. Additionally, the game may require a significant time investment to reach higher competitive levels or complete event challenges.

8. What other games have been developed by the same developer:
Konami, the developer behind Yu-Gi-Oh! Duel Links, is a well-known video game company responsible for a plethora of titles. Some notable games include the Metal Gear series, the Castlevania series, the Pro Evolution Soccer (PES) series, Silent Hill series, and other card game adaptations such as the Castlevania: Grimoire of Souls and various Yu-Gi-Oh! titles across multiple gaming platforms.