Bonjour Yann -
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The rank title "second officer" is not well defined. It varies airline to airline, country to country.
With United Airlines in USA, they called their pilot flight engineers "Second Officers".
Here in Argentina, a "Second Officer" is a "cruise co-pilot" in a crew of 3 pilots.
They occupy a pilot seat during the period of rest of the captain, and when the First Officer is in charge.
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As to licencing, most countries will issue a type rating, but will specify the rating to be valid as P1 or P2.
Generally, the "First Officers" who fly as "cruise captain" are fully type rated.
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Hope this helps - I dont know exactly how CX does...
Happy contrails