When will current pass through when applied a reverse voltage Vr?

Those were good answers. You asked when? As the reverse voltage is applied there is a few nano seconds, before you get a fixed reverse current flow = perhaps one nano amp for modern diodes and transistors. The leakage current increases slowly as you pass the rated reverse voltage, then increases rapidly to damage the diode or junction, unless you are using a current limited supply. Typically about 1/10th watt dissipated in the reversed biased junction causes hot spots which permanently damages the junction. Now the device has new specs, usually much inferior. Some junctions behave like a zener diode and can dissipate a watt or more without permanent damage. Neil