Can the first-class third officer be a second-class driver?

Of course. A first-class third officer (first-class pilot) who has served on a first-class or second-class inland river vessel for 36 months is deemed to meet the requirements for a second-class pilot to apply for a second-class captain, and may directly apply for a second-class captain. The first-class third mate refers to the first-class captain, first mate, second mate and third mate, and is only applicable to inland river vessels under 1.600 tons or 1.500 kilowatts.