No, you can't. The Adelia locks the axles together on acceleration, it would totally negate the Tarmac. The Tarmac is literally the worst thing on earth for a gravel car, since it's a rear-biased open differential. That means that when one axle has no traction, all the torque goes to that axle and you go NOWHERE (assuming you have no coupler attached). A stock differential with stock viscous coupler would be more effective than the Adelia, since it would allow the Tarmac to do it's thing and overpower the rear tires until the coupling clamps down, plus you wouldn't have to pay anything for it. I understand your line of thinking - you want a rear-biased setup that still powers all 4 wheels, and the front axle can pull you out when the rear tires spin. True rear-biased AWD is only possible on hydraulic setups and modern clutch-actuated setups, or with planetary center LSDs like the Audi Quattro system. The closest you could get would be to use a stock viscous coupling on the Tarmac, which would allow some spin, but you have essentially no control over when it locks, or unlocks, which is problematic. The coupler's condition could also deteriorate and make it useless (if it's not already shot). The second best thing I could recommend is to get an ATS or Cusco plate-style center diff and mess with the preload from front to back. You might be able to give the rears a bit more liberty in terms of lock delay and breakaway torque to allow it to spin up before locking all 4, but it would take a lot of trial-and-error to get it right. The plate-style center diffs can allow you to cheat a bit, since they are 2-way. They have a locking effect on deceleration too, which allows the rear to rotate into a corner before you get on the gas, and could be amplified by a 2-way rear differential. All of that just destabilizes the rear before accelerating, which is akin to having a rear-biased setup that will destabilize the rear on acceleration only. If it's power-on oversteer you're after, it's very difficult to find in our cars. Our diff sucks.
If you have the Adelia, use it on a stock center diff and find a different way to get the results you want. The Adelia is essentially untunable. You can remove some ball bearings to mess with the preload a bit, but you cannot change the front-rear bias of it. Just stay stock if you don't have the coupling.