You can’t fly an 737-200 for 3 years and then jump into a 737 NG without difference training. You won’t know how to work the flight management systems. They ar

You can’t fly an 737-200 for 3 years and then jump into a 737 NG without difference training. You won’t know how to work the flight management systems. They are the same type, so you don’t need to re-qualify for the type. But you need to do training to move between variants of a type. It’s just a lot less training.