I want to order a mobile application, what should I ask the developer to understand that he can make this product?

Question

Android

In short, I will describe what I need. The application will load the video after watching the video there will be a question about the content of the video. the user answers the question, he is sent a serial number and that's it.

Answer 1

Describe the application and ask if he can do it.
And how long will it take. Another important question is "Where will your video be located and how many videos will you have?" If the video is on the server and you will add a new one every time, then the server part should also be done by someone. and it will take longer. If your application is very simple and does not require a server (there is only one video), then it should be done in a maximum of 5 days. But judging by your description "serial number is sent to it" the Server all the same should be. And someone has to administer the server part (Upload videos, write questions about the content, keep track of serial numbers), it turns out you need an admin panel, which means another application. Professionals will do it quickly, professionally :-D but more expensive, then it's clear.

Answer 2

Ask him for a portfolio. Install and poke the apps he developed.
Asking some technical questions, IMHO, is stupid, you don’t understand android systems, as I understand it.
Well, the freelancer profile speaks for itself.
PS I must warn you that android and video are hemorrhoids. Good luck!