Are French and Italian very useful languages to learn?

French used the be the official language used by diplomats back a hundred years ago. Unless you got a career in the fashion/modeling industry, it's no use learning French or Italian (except for cultural enrichment.)

Depends on how you define "useful." Do you want to live in a country that speaks those languages? Do you want to be able to read the literature of those countries or maybe current newspapers and blogs in those languages? Are you interested in doing business with companies in those countries? Or what?

French, yes, especially if you plan to travel or to go into law. Italian, not so much.

Fairly useful in some parts of the world. Very useful in France and Italy respectively.

spanish is most usefull.

reason : it is the second most spoken motherlanguage after chinese.

That also means, that spanish is spoken in most countries on the planet.

Basically apart from Spain, all south american countries, but Brasil, speak spanish.