what does that yellow light mean also the image with the axle in it ?
1st one diff lock
Second exhaust or engine break engaged if you driving and this is flashing move the right hand stack towards the dash and which will shut it off or move it to positions one or 2 for engine braking better to do this in manual mode and have your revs at the top of the green or better in the yellow
What truck
Axor by the looks of it
yep its an axor.
MSS is stop start - just like in the car. Can be useful in major traffic jams. Engine turns off when handbrake and neutral applied and comes back on when you press the clutch.
diff lock as mentioned above it.
exhaust brake as mentioned. stops you picking up as much speed going down hills and saves wear on the service brakes. the higher the revs on this the more effective it is.