Hello,
In the past I have created scheduling and publishing tool for Instagram (and other social networks like Facebook, Twitter, Pinterest) platform via mobile app, and following the different iOS and Android privacy policies based use cases.
We did it using platform specific SDKs (because the project requirements were only limited to mobile), and checked the Instagram APIs for web technology frameworks during the course. Therefore we have hands-on experience of scheduling and publishing posts on different platforms and can use the experience.
My previous experience of your relevant scope is already a small part of a complex project at that time. Therefore, your requirement is pretty much straightforward for us, and can create a robust tool.
I recommend building this tool using Laravel, and can share previous experience/information in private chat.
I have few questions before finalizing my proposal, let's discuss in private chat. Right now it's the placeholder.
Looking forward to hearing from you.
Thank you.
TOPS Infosolutions.