Question: Is it possible to know if the email sent for a specific user was opened first from a mobile device?

Answer: 
You can get device information but user-wise device information can't be obtained. So, which subscriber opened the email on which device can't be obtained as far as I know but how many subscribers opened or clicked on a particular mobile device or computer/laptop can be obtained from SFMC reports.

[![enter image description here](https://i.stack.imgur.com/qFm1q.png)](https://i.stack.imgur.com/qFm1q.png)

This does not quite answer the question because the report does not specify 'email sent for a specific user' but 'Blank Template for Email sending performance' can be used to get a lot of user tracking information.
As far I know, this functionality doesn't exist in SFMC. We use third-party tools to track that.