To determine wheteher the 18650 li ion is protected battery
A protected LiIon battery will disconnect the output of the battery to prevent overdischarge. It also has overload protection. You could do one of the following:

Discharge the battery using a resistor. If the battery voltage drops below 2.3V, then the battery is not protected.
This test is only for the bold: Connect a slow blow fuse, e.g. 500mA directly in parallel with the battery. If the fuse survives, then the battery is protected, because the protection circuit should protect the battery from short circuits.