How to install a developing public app on managed store

[CSSHero]

Hi, we're building an app and we would like to test it on a proper (non development) store.

Problem is that when we request the shop frontend page via api we get a password protected page hence we can't complete our development.

Question is: how can we run an under development app on a (paid) managed store that we plan to use only for dev purposes? Alternatively is there a way to get around the password wall via fetch?