yes there are helicopters which can dump fuel. the most basic helicopter allouette ( the french single engine helicopter) has a capability of jettisoning fuel at the rate of 130 lts per hr.
Not any as far as I know.
The type of fuel is specific to the type of engine, not the aircraft. Helicopters that have jet engines use jet fuel, and helicopters that have internal combustion engines use gasoline. However the General Electric T-58 had a device in the fuel control that allowed you to burn just about anything from avgas to jet fuel to kerosene.
Gasoline or Jet 'A'
We would need to know what size or model plane you are asking about. They are located under the fuel cells, if they have them. Not all planes can dump fuel.
Yes, they do. Just as cars, do in tanks.
most of them use standard military jet fuel
Most larger trucks burn diesel fuel.
Most helicopters used a kerosene based fuel, such as Jet A, Jet B, or - in the case of military aircraft of NATO countries - JP-8. However, helicopters which use internal combustion engines will use standard 100 Low Lead petrol fuel.
No.
In general: no, not on a normal flight. Any fuel "left over" in the tanks will be used for the next flight. Airliners only dump fuel when they are too heavy to make a safe landing - and this situation only occurs when the landing happens much earlier than planned, such as a diversion or an emergency landing. Not all commercial airliners can dump fuel, some have no option but flying around for a while to "burn off" fuel before being light enough to make the above-mentioned early landing.
Yes, many small helicopters have 3 blades
turbine helicopters take either JP-4 or JP-5 grade jet fuel.