I have sincerely enjoyed going through the beginnings of this thread and listening to your little snippets of music - the development of Thing to Thing2.0 was a pleasant surprise and I love how much effort you've put into this. There were even some rhythm changes and a key change along with the instrumental variations in Thing2.0 and I was not expecting anything as complex from how you were talking - please don't underrate your own skill when it comes to composing. Perhaps you have a lot to work on, but it seems you've done a lot already.
I'm actually not sure what parts a flute is meant to perform, but they sure sound nice
As for this, when a part of song composition, a flute will traditionally play along the melody or separate a distinct harmony, some of a different tempo to the song to offset other instruments on the main melody line. Higher or lower pitch is your game. Don't worry about where an instrument is "meant" to go though - if it sounds good, it's in the right place.
Is This How You Violin is a nice little piece too; and if you're going to improve upon it, perhaps slow the beat a bit? All of your trials seem like fast and upbeat songs, but from what I've heard of this new little snippet, it could use a bit more rest.
Well done again and keen to hear more!