We have it fitted to one or two of ours, it is a DAF thing which can be switched off using a laptop, you will also find that the throttle pedal goes limp if the clutch is not fully engaged, so the trick is to get it rolling on tick-over, clutch out and then apply some gas.
Not sure reversing in high range is a good idea in any truck, you’ll have more control in low range (I’m sure I read in a manual (Scania?) that it’s not advised anyway) and it’s kinder on the clutch and also the fifth wheel and pin if you’re hooking up, rather than trying to break it.
As for changing from 2nd (hi/lo) to 5th(hi/lo) is a no no, as even in a CF380 unladen or a XF410 unladen, they don’t really like it. as someone else has said go 2 to 4 then high range 6 to 8, that’s only 3 gearchanges and your in top, 4 if you have a splitter.