If you book a Blue or Blue Extra fare and cancel, your points would be returned to your account and any cash that you paid would be returned in the form of a Travel Bank credit. There are no restrictions other than just needing to cancel before the flight departs.

The difference between Blue and Blue Extra is early boarding, free same-day switches/standby, and expedited security (where available) for Blue Extra bookings. There is no difference between them in terms of refundability/points redeposit.