1. **Introduction of the game:**
Kick the Buddy: Forever is the sequel to the infamous stress-relief game Kick the Buddy, which revolves around a sandbox approach where players utilize various weapons and items to inflict damage on an animated character named Buddy. Players are given a canvas to vent their frustration, using an array of imaginative tools to 'kick' Buddy, with the violence depicted in a cartoonish, non-realistic manner.

2. **All characters and levels of the game:**
The central character of the game is Buddy, an invincible ragdoll that bears the brunt of the player's attacks. As for levels, Kick the Buddy: Forever doesn't have traditional progressing levels but instead offers a continuous gameplay experience where players unlock and use new weapons and items to interact with Buddy in ever more creative and destructive ways.

3. **What attracts users most to the game:**
The sheer variety of ways to interact with Buddy is what attracts most users. The game offers a cathartic release, with an extensive arsenal that includes firearms, explosives, sharp objects, fantastical magic spells, and even natural disasters. The humor and the satisfactorily visual and sound effects also add to the game's allure.

4. **Why it is popular:**
Kick the Buddy: Forever gained popularity due to its simple and addictive gameplay, coupled with the comedic relief it provides. Its appeal lies in the ability for players to relieve stress without consequences, engaging in destructive scenarios that are imaginative and exaggerated in a whimsical, animated universe.

5. **When the game was released and how many versions are currently available:**
Kick the Buddy: Forever was released in December 2018. There have been updates to the game since its release, but as far as distinct versions go, it primarily exists as a single, regularly updated edition. It follows the original Kick the Buddy game, essentially making it the second installment.

6. **The most difficult part of the game:**
Since the game is designed more for entertainment and stress relief than for challenge, it lacks traditional difficulty levels. However, the most challenging aspect could be considered unlocking all the available weapons and items, as this requires consistent play or in-app purchases.

7. **Strengths and weaknesses of the game:**
Strengths include the game's wide array of choices for weapons and the simplicity of the gameplay, which makes it accessible for players of all ages. The weaknesses are the repetitive nature of gameplay, which may not appeal to players looking for depth or progression, and the reliance on in-app purchases for faster access to the game's content.

8. **What other games have been developed by the same developer:**
The developer behind Kick the Buddy: Forever is Playgendary, known for creating casual and arcade-style games that are typically easy to pick up and play. Their portfolio includes popular titles such as "Bowmasters," "Tank Stars," "Polysphere," and many others, all of which share a casual, player-friendly approach with a focus on simple, engaging gameplay mechanics.