  Quantum resources may provide advantage over their classical counterparts. We
say this as quantum advantage. Here we consider a single task to study
different approaches of having quantum advantage. We say this as a unified
scenario. In our task, there are three parties: Manager, Alice, and Bob. The
Manager sends a value of a random variable to Alice and at the same time Bob
receives some partial information regarding that value. Initially, neither
Alice nor Bob knows the input of the other. The goal of the task is achieved if
and only if the value of the random variable, sent to Alice, is identified by
Bob with success probability greater than half all the time. Here error
probability is non-zero. To help Bob, Alice sends a limited amount of classical
or quantum information to him. We show that the goal of the task can be
achieved when Alice sends a qubit. On the other hand, a cbit communication is
not sufficient for achieving the goal. Thus, it establishes quantum advantage.
We further show that the optimal success probability in the overall process for
a qubit communication might be higher than that for a cbit communication.
Clearly, it not only establishes quantum advantage, it also demonstrates a more
prominent non-classical feature. We also obtain higher success probability
compared to other tasks. This suggests the experiment friendly nature of our
task. Then, we connect our task with semi-device-independence and show how our
task can be useful to detect quantumness of communication securely. Similarly,
we provide a way to detect universal coherence of an ensemble. For a high
dimensional random variable, to achieve the goal, it may require an arbitrarily
high dimensional classical communication while it can be achieved by sending a
qubit only. This establishes an arbitrarily large quantum-classical separation.
