Shopify has an api
Is Shopify app-based only?
Shopify is a Sass Platform, so like a hosted wordpress CMS they provide an ecommerce admin with a CMS, and manage the hardware infrastructure.
Third parties use the api to build apps to increase the capabilities of the platform.
You do not need to worry about the API access as its based on permission and you can revoke the permissino anytime
But you should still let someone whom you can trust to provide him access
If you are looking for support in terms of app let me know email@example.com