Can i achieve the same thing ny 'Force AC mode' from hijack ?
Mostly. However, this requires that you personally intervene (go into hijack and change the setting) every time you move the player between home and car. It doesn't happen automatically.
Also, from-scratch flash upgrades on power-application still won't work from the car dock in that case, since the power-on-boot flash runs before hijack runs (as described in the FAQ
here).
I prefer to have the hardware do the home/car detection. That way all of
these behaviors kick in automatically when move it between home and car, and I don't need to do anything (such as changing hijack menu settings) when I move it.