Can the qiskit function QuantumCircuit.initialize be used to initiate any number of qubits (which exist currently on the quantum computers) and can it be used on a real quantum computer?
The initialize method uses an algorithm to generate a set of gates that implement your input statevector. Therefore it can also be used on real hardware. But it is important to note, that this is a generic algorithm that works for any statevector. There might be much more efficient preparations for your particular case. You should definitely check if there aren’t too many gates generated, before running initialize on real hardware. State preparation is still an active field of research.