Hello, we are developing an app for a client’s store and need to deploy what we have so far to their store even though it is still in heavy development, and will never be available in the app store
A nice step by step would be most handy at this time
Hi @nucleo 
Generally, apps still in development should be tested and staged on a development store. We have a guide here for getting started using Shopify CLI, that includes local deployment and installation on a dev store.
For apps intended to be installed to a single Shopify store, it would be built as a custom app type from a partner account or the merchant Admin. I’d recommend reviewing the requirements for each app type to ensure that your app has appropriate authorization/authentication practices.
Hope that helps!
Sorry for the late reply, thank you for your information, i managed to work it out, thank you once again