why does antimarkownikoofs rule is apllicable to only Hbr and not hcl and HF or HI please explain the concept in detial
With the other hydrogen halides, the opposite is true.
The hydrogen-fluorine bond is so strong that fluorine radicals aren't formed in the initiation step.
With hydrogen chloride, the second half of the propagation stage is very slow. If you do a bond enthalpy sum, you will find that the following reaction is endothermic.
This is due to the relatively high hydrogen-chlorine bond strength.
In this case, the first step of the propagation stage turns out to be endothermic and this slows the reaction down. Not enough energy is released when the weak carbon-iodine bond is formed.