Hi,
Voltage limit:
5V supply goes to Q2 base. The emitter is 0.6V less = 4.4V
But when the output voltage is high enough (@ 4.4V + 8.2V = 12.6V) then Q2 emitter will be higher than 4.4V making V_BE less than 0.6V and thus Q2 switches OFF.
Current limit:
Voltage across R2 is 4.4V making 0.94mA of emitter current. Collector current is slightly less.
So if Q1 h-FE is 100 (just as example. Didn´t read the datsheet) then the output current is limited to 100 x 0.94mA = 94mA.
Klaus