I have two questions: can I post my video on IGTV instead of YouTube? And can I demonstrate my music implemented in a middleware?
can I post my video on IGTV instead of YouTube?
Yes, but would be great if it's on Youtube as well.
can I demonstrate my music implemented in a middleware?
You mean something like Fmod and Wwise? Yes, but that's not exactly necessary, but if you want to go all out with it then feel free to! You still need to submit the original recording though.