The were never tested. There were no decisive battleship fleet actions fought during WWI. Only battlecruisers and cruisers duelled heavily against each other.
About a year.
Dreadnoughts.
COD 1 :D And battleships of corse
They were all sunk or scuttled (intentionally sunk).
No, Britain did not build any battleships for Turkey during World War 1. However, they did build and deliver two dreadnought battleships for the Ottoman Empire (which included present-day Turkey) in the years leading up to the war. These were the Sultan Osman I and Reşadiye, which were both commissioned in 1914.
They weren't battleships, they were obsolete and redundant World War 1 destroyers, and they weren't 'given', they were lent under the Lend/Lease Agreement and had to be either returned or paid for at the end of hostilities.
See website: WW1 for a itemized list
Yes, airplanes fought in the air, and battleships, cruisers and submarines fought at sea and under it.
The USA joined in the war because the USA was part of the Triple alliance in the first place, and after Germany attacked the USA's submarines and battleships, they then joined the war in 1917.
Basically, a battleship is typified by large guns, and thick armor since the late 1800's. In World War 1 battleships also carried torpedoes and a variety of smaller guns, but they never got close enough to use them, and these were done away with.
No, not as ground forces, although they did serve in France during World War 1. US Navy battleships and cruisers in the European Theater during World War 2 would have typically carried a small number of US Marines.
I'm sure you mean "attacked", and I think you mean "warships", not battleships. I'm also sure the answer is "none", if you mean during the period leading up to the entry of the US in WWI.