Can aileron differential eliminate adverse yaw?
That depends on flight speed.
Adverse yaw is strongest at low speed. A high-aspect ratio configuration will not be able to avoid adverse yaw, regardless of the degree of aileron differential.
At high speed the same airplane might roll fine without rudder corrections, because then aileron differential will be able to compensate for the then low adverse yaw if enough differential is provided.
Depending on airfoil rear camber, adverse yaw is also good for reducing aileron control forces. Again, the effect varies with speed and will result in a high degree of force reduction at low speed while forces are still high at high speed. The need to keep aileron forces growing with deflection angle is normally the limit for aileron differential, so it is impossible to tailor differential to overcome adverse yaw at low speed even for wings of moderate aspect ratio.