NO it's NOT normal!
Shouldn't be losing ANY water.
Correct but level can and does vary with expansion and contraction.
the temp gauge should sit at the half way mark when the engines up to temp, maybe just a bit below on high speed runs, not at quarter though have the thermostat checked/replaced.
I have known my temp gauge to pluumet right to cold on long distance runs from normal running temp. on 30 mph roads. I am assuming this is nor errr "regular", then.
Why does every other owner immediately think 'head gasket' whenever something appears not right. We've had some very cold overnight temperatures recently and remember coolant not only expands when hot but, contracts when very cold. If you check the coolant level regualrly over many months in both hot summers and cold winters, there will be a fair degree of level movement depending on when you check the level. Unless there is evidence of sustained coolant loss, don't worry but keep an eye on things and check for leaks. Expansion bottle cap renewal is always a good idea. The do not last forever and do progressively deteriorate being subject to both big temperature and pressure variances so wear out over time.
Temperature gauge needle sudden drops ... Not normal at all.... My K and T series cars are ALWAYS steady at a tad below half way on the gauge. If you have any big fluctuations from that once fully warmed up, a dodgy thermostat would be where my money would go on.
Only on one occasion have I know a temperature gauge to plummet on a long run. That was about 30 odd years ago driving high up on the Cotswolds in a Mini 1000 on what was one of the coldest winter days I've ever known. Driving NE straight into an artic wind I actually felt the little car slow as the NE wind gusted strongly. Glancing at the temperature gauge I saw it near 'cold' although I'd been driving half an hour. I had a sheet of thick cardboard in the boot and wedged that behind the grill which helped a bit. The rad on the Minios was located in the nearside wing area.
Never did it again but, I suspect the thermostat needed changing as the car had done 95,000 from new still on original thermostat.
EDIT @ 1522 ... I hate the winter .... Roll on March.