No I wasn’t missing the point. It was the other guy failing to give a simple straight up answer.
The images in your original post make it quite clear that Instagram is rejecting your submission because they suspect it contains copyrighted material: and as I explained songs you purchased in iTunes are copyright and cannot be used without a written permission (which you are not likely to get). iMove will reject songs with DRM (protection) but iTunes songs are no longer sold with this - that doesn't mean that they are free to use. Instragram is very properly requiring that you provide proof of permission to use this material, which you evidently haven't got. If you cannot get written permission you will have to remove the music. That's as straight up as I can make it.