Hello,
Consider an app on your cell phone. For example, a program that shows you the best driving route or a diet plan. Do these programs carry out all the instructions on your mobile phone or are they just an interface that connects to a remote server and processes and algorithms are executed there and the result is shown on your mobile phone?
Well i’m not exactly a dietician or have knowledge of the features or calculations involved in such an app because I’ve never developed one. I can’t answer those 3 questions for an app I’m not designing or developing, and the needs of the program would depend on the answers.