Simple On-Prem Data example

I'm looking for very simple O365 SharePoint Development examples to cover these types typical needs as we move SharePoint to the Cloud:

* SharePoint Online custom Form with jQuery code that pulls on-prem data from an SQL view into a dropdown control?

* SharePoint Online DataView joining to on-prem data from ab SQL View

* On-Prem ASP.NET solution consuming O365 SharePoint List Data

Looking for minimal code, big picture, high level step explanation and options.

High level question, but how would Claims Based Authentication, oAuth, oData, REST and an ADFS server fit into any desired Security/Authentication Scheme to help address those 3 needs?

Thanks.