>"excluding Google, YT, FB, other search engines and other inappropriate sites for a more insightful map"

Either you exclude every:

• Search engines
• Social media
• Video sharing platforms

or you don't exclude any.

Excluding Facebook but allowing Twitter makes no sense to me.

Technically right, but completely wrong when it comes to actual real life use.

I have never encountered a single French person who uses anything but their first name as their "Prénom usuel".

Once again, these terms are only use in an administrative way and are (almost) never used in any other context.

No.

The same thing said with "Prénom" would be interpreted as "Premier prénom" by default.

As I said, "Prénom" always means "Premier prénom" unless stated otherwise.

And my point is that, unless stated otherwise, "Prénom" means "Premier prénom".

Yes, but not a single french person will ask you your "Premier prénom".

When asking for someone's first name you simply ask what is the person's "prénom", and if you want to ask about if they have a second or third name then you simply ask about what their "second name" is or if they have other "prénoms".

But this is not asked often at all, as 2nd and 3rd names are only ever used in an administrative kind of way and never used to actually talk to someone.