I know that it was a long time ago, but only for the record.
Since this requires public_scope permission (a permission that gives you access to all publicly available data on instagram, not just your account), your application needs to be verified and approved by Instagram. However, if you use the API for a personal project with one site, Instagram will not approve it.
Here from Instagram docs:
1: Which use case best describes your Instagram integration?
R: I want to display hashtag content and publicly available content on my website.
A: This use case is not supported. We do not approve of public_content for one-time projects, such as displaying hashtag on your site. As an alternative, you can show your own Instagram content or find a company offering this type of service (content discovery, moderation and display).
You can find more information in the permission documentation.
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