Do I need to take specifically the train on my itinerary?

No, you don't. You might find suggested train times on the itinerary of your journey. These train times are recommendations according to the times of your flights and it’s not necessary to specifically take the train marked on your itinerary.

When you check in on Deutsche Bahn’s site for your train ride, you can choose the train connection of your preference, and your train ticket can be used flexibly as long as:

• it is used on the selected day of travel,
• it is used for the route in your booking and
• it is not issued for a specific train.