I had a neat idea for a project which would involve posting to Instagram feeds so I looked into the API and there is basically nothing you can do to create posts programmatically.
I know it's their platform but I was still surprised at how locked-down it is.
Why don't they let makers interact with it like Twitter does?!
/Rant
They are not even accepting new partners that can have that access. If possible, you can also automate mobile version of instagram.com with a browser automation library like puppeteer. That's what I had done.
However, that may not work well with a lot of Instagram accounts.