plagiarism: Basically copying something from the internet, and or from someone story, books, etc.
inspiration: u have the motivation to write what u love to write about, u have everything planned and not copied from someone else. U inspire others to write, or u get inspiration from someone who write what u love to read, etc.
Well to be honest that description sounds like Total Drama Island , I think pretty much most comedies about reality shows play out like that. If those are your only reasons I dont see that as plagiarism
I think the points that you mentioned as similarities are very general tropes or characteristics and doesn’t straight up lead to plagiarism. However, only YOU can know if you really copied that story or not. Did you come up with it yourself but it coincidentally already existed in another story? Or did you just add those things to your story because you took it from another story. The latter, doing that is fine depending on what you let yourself ‘inspire’. An evil leader is nothing new, but make sure you don’t make him the exact same person as the one in Galactic Game. After all, just evil is not what makes a person. An evil person has many more things and traits to them just like any other. Sketchy things happening in your story and throughout the game is nothing anyone can claim copyright infringement for. But if said sketchy things are the exact same kind of things happening as in Galactic Game, then you’re walking on a very thin line of plagiarism. Hope that made sense! Just make sure that YOU know you didn’t literally copy it. If anything, if you did you’re the only person who knows what wasn’t your own idea and you can always tweak it or add a twist to it so it becomes your own idea by taking inspiration from someone else’s work. Instead of making the leader just evil, make him be the father of one of your close friends/love interest in the game - just to give an idea.
However, if you feel you got heavy inspiration from a story, it would be great common courtesy to let your audience know where you drew the inspiration from. Otherwise, trying to cover up the origin of inspiration can come across like you were trying to plagiarize.