Question 3 I cant give you a drawing, but I think you should have no problem drawing your own from the description.
The most common method uses two lamps, both suitable for the full switchboard voltage. The lamps are connected together in series (through fuses) from both the positive and negitive busbars. The centre point, between the two lamps, is connected to the vessels hull (earth).
If the insulation is good, both lamps will glow with equal "half" brightness. If the insulation is bad the lamp on the effected side is short circuited (dark) and the other lamp will glow with full brightness, due to the current flowing through it. The bigger the difference in brightness between the two lamps the bigger the earth fault.
The trouble with this system is that a slight earth fault on both phases will not show up. To help avoid this problem a switch can be placed in each cable to the lamp. If a earth is present the bulb will glow brighter, when one switch is opened.
To find the earth, simply isolate the equipment piece by piece keeping an eye on the lamps. Remember the one that goes dimmer or dark is the effected phase.
Question 2 - sorry, not sure on this one.
Question 1 - There are probably many different answers to this but here are a few suggestions;
hose test - prove watertightness of watertight doors or flap, can also be used to prove a bulkhead repair has been done satisfactorily. Generally done with a fire hose.
head test - (not heard of this one) Possibly to prove water tight integrity of a tank, fill the tank to the top of the vent, this is the max head that the tank should take without leak or distortion.
drop test - I know of one test, carried out on a new anchor. The anchor is dropped from 12ft onto an iron slab. If it doesnt fracture the anchor passes.
hammer test - Can be used to check if nuts/bolts etc are tight and gives a clear ring for tight and a dull thud for loose. Can also be used to check for cracks in springs etc... again, a clear ring is good, and a dull thud is bad.
Hope that helps