I'm wondering if I do an arrangement of a song that I received, does that count under the rule of using at least one song that I received?Like changing the key or adding some mix, etc.
To be clear, you do not have to play the actual music in the game. When we talk about “using” the music, we mean it more abstractly, in that you will you use the music for inspiration in writing the game.
The game submission will ask you to list the songs that the game is based on, and in the rating phase, judges will be asked to rate games based on how the ideas from the songs were incorporated.