Yes, you can get full refund.
From
flying blue website:
You can cancel your reward ticket or Promo reward ticket without having to pay a cancellation fee under the following circumstances:
- if your reward flight has been cancelled by the airline, or
- if the travel date of your reward flight or Promo reward flight is on or before 31 March 2022, and
- your request for cancellation is made before departure of the first flight.
Both Miles and cash will be credited. Please note that ticketing fees are non-refundable. Original ticket conditions apply for cancelling other reward tickets and Promo reward tickets. Contact customer service to cancel your flight.