To Mockup or to Prototype?

Hi Indie Hackers,

Recently I came by a problem as a customer of a service that I think could be solved through an app that is distributed by the company. I'm thinking of making a white label app that could be licensed to the company. However, I've never done anything like this before so I had a few questions.

1. I don't know if the company will be willing to adopt this so should I approach them with a mock-up or an app prototype. Mock-up would definitely be less effort but I'm wondering if it would be less convincing than having a finished app?

2. If I go ahead with an app, would a no-code solution or coding in Swift/React Native make sense?

3. Any no-code recommendations to publish to the app store?

4. What would your pricing structure be for a B2B2C app? Would you charge per user account created or a fixed licensing fee per year?

Thanks,