In many forums, information on the used software or whatever helpful.

That's why I think it would be good if you can query at the start of a theme. Or if you can force these details (optional).
The information should be displayed in the first post. And (optionally) on the board. See screenshot attached.

In the admin panel should be able to specify the number and content of the fields.

Note: The Schreenshots are not by an modification. The changes were made only in Google Chrome Web Inspector.

I think there's already a free mod for this, isn't it?

By name yes. In function not.

Which one?