Hey, welcome to the ESRI community! This indeed is the place to get answers to all things ESRI.
Arcade can not be used to call stored procedures. It simply doesn't have any functions to do that (and I have no clue if it could theoretically be possible).
Arcade can be used to read and write data to tables. These write processes also execute database triggers.
Should/Can Arcade be used to develop the app
You can't develop an App in Arcade, it isn't made for that. Arcade is a language ESRI created for interacting with data in many (all?) of their applications: For example, you can
- populate map popups
- make labels and symbology dependent on feature attributes
- build datasets for charts in Dashboards
- implement Attribute Rules (similar to database triggers and I think Batch Calculation Attribute Rules and Validation Rules function similar to stored procedures)
So you can't develop an App in Arcade, but Arcade could play a role in your App, depending on what you want to do.
I'm not certain how implement a mobile app
Depends on what you want to do.
Do you just want to show a map? Then a simple Webmap might suffice.
Do you want to add some functionality around that map, e.g. feature filters, measuring tools, info graphics, bookmarks, sharing, splash screen, data editing, and then some more? Web AppBuilder can do that.
Do you want even more, like multiple pages, embedded Dashboards, dynamic feature lists, completely free layout? Look no further than Experience Builder.
If that isn't enough, you have to develop either widgets for a prebuilt ESRI App or your own custom App. I think most people do that with the ArcGIS API for JavaScript. Give the community a look!
As for the role Arcade could play in all of this, maybe this blog can answer some of your questions: Your Arcade Questions Answered (esri.com)
For better directions, it would be helpful to know more about what you want to do.
Have a great day!
Johannes
