you cant put the batteries in the wrong way around in a mk3 collar, well you could but it wont close together, they fit one way only...
going back to the pin point control on the back, its more than just a volume control
first off though, get some electrical tape and stick it over the speaker holes, trust me, if you dont reduce the whinning bleps coming from it, you'll feel like captain kirk with a fazer gun
whilst in search mode, your getting the bleeps, turn the pinpoint control knob, so the bleeps on just disappear, now take a step forward,left,right,back, you'll only hear blee