I am trying to fetch the response of request "api/2020-04/inventory_levels.json". But I am getting response
If you need access to a particular resource, the merchant will always need to approve this. If you don't want to use a private app, you can use a custom or public app instead. Both public and custom apps use Oauth, so the merchant approves during initial install. If you need access to additional scopes after an Oauth install, you can redirect merchants back to the Oauth screen to approve any extra scopes.
Custom apps are apps that can be embedded in the Shopify admin, they're only meant to be installed on 1 store and aren't subject to review by Shopify.
Public apps can be installed on multiple stores, with the option to list the app in the Shopify App Store. Public apps are subject to review before they can be installed.
The URL looks like this:
It's the same URL you direct users to during install. You can redirect back to this URL anytime with additional scope params, and this will prompt the user to accept the new scopes. More info in our OAuth doc here.