If it has a slit in the side of the pin, it is because it was made from flat material that is rolled into a pin. If it were solid. there would be no slit or seam.
The little slit in the pins makes it flexible when it is inserted in the socket. It helps to make a good contact adjust itself in the socket.
The three pin plug is grounded (provided the receptacle is wired correctly).
Would that be the smallest pin. To answer this question the specifications of the plug will be needed.
No, it is not ok, it is potentially very dangerous because the two-wire cable has no earth with it. The earth wire is an important safety component that comes with a three-pin plug. An exception can be made for certain low-power appliances that have double insulation. This includes TV sets, radios, and table lights provided the mounting is plastic and not metal. These appliances are commonly sold with a twin-wire cable but often with a three-pin plug on the end of it. The three-pin plug in this case often has a plastic 'earth' pin and it is safe to replace it with a two-pin plug.
Need more info. There are three pin plugs at a wide variety of voltages.
it is the brown wire in a three pin plug
The ground blade is the longest in a three blade plug.
UK answer only: Yes but you need a three-pin to two-pin adaptor. Alternatively fit a three-pin plug to the light and leave the earth pin disconnected. This can only be done if the lamp already has a two-wire cable fitted to it, anything else is potentially dangerous.
On a UK three pin plug the two smaller prongs are Live (brown) and Neutral (blue). The Larger pin is for the Earth wire. This can prevent you getting an electric shock
In North America the neutral pin is used to complete the circuit. One pin is "hot", one pin is neutral and the last pin is ground.
Standard UK three pin
The standard domestic electricity supply in Ireland is 230 volt AC (frequency 50hz). The most common plug used is the 13 amp three-pin plug.