Rather than try to return the entire first stage to Earth, Adeline carries the most expensive rocket engine and avionics. The machine has an aerodynamic shield that reduces engine stress on the way down, and two winglets with rotary motors to guide the craft safely to the ground -- Airbus envisions the rocket segment landing on runways, not launchpads. This approach reportedly requires much less fuel than SpaceX's approach, and would lop as much as 30 percent off routine launch costs.
They are hoping to be operational in 2025-2030.
The current next generation Ariane 6 will fly in 2020. Modifying it to include the Adeline will not occur until after it is flying.
Adeline only exists as a scale prototype right now.