No.
Don't reupload other's work.
For the extensions: use the loop button.
No.
This is the same as reuploading, but with low effort effects in Audacity.
No.
If you want me to make music for a game, please ask on Twitter, email, or Discord.
Sure, but do the steps below.
Sure, but remember to credit me.
Link/name the music you used in the description, comments, in the video, wherever so long as it's clearly visible.