Also ich shreibe auf english besser, weil es gehts fuer mich besser. 
 
The wire (grey/blue 0,35mm2) from Pin 29 BCO to Pin 3 in front light really is just a spare wire. It has no function what so ever! I guess it is designed for some future updates and retrofits. 
 
I went to garage, double checked my front light for right function and it works perfectly:
After that I removed the plug from front light and looked it over - There is no corresponding pin in the front headlight for the pin 3 in the plug!
So the question about what 58P2_12V does is solved. Nothing. 
Few pictures in attachment for better understanding:
Conclusion... The retrofit and coding is safe and can be used without worries! 
 
 
Coding for rear light retrofit:
gen_LightModules_Freq: 100_Hz [00 64] -> gen_LightModules_Freq: 
200_Hz [00 C8]
led_fibl_active: not_active [00] -> led_fibl_active: 
active [01]
pol_UseFrontPosLightForBrakeLight2_Enable: Not_Active [00] -> pol_UseFrontPosLightForBrakeLight2_Enable: 
Active [01]