Champagne is the only fictional ship. The others in the bottom tier are all WWI ships.
HMS Cheshire was launched on April 20, 1927 as a passenger ship but was requisitioned by the Admiralty and converted into an armed merchant cruiser. She was torpedoed twice during WWII but survived both times, and was used as a repatriation ship at the end of the war before being returned to her owner in 1948 and eventually scrapped in 1957.
HMS Monarch was an Orion-class battleship launched March 30, 1911. She participated in the Battle of Jutland and survived the war, but was decommissioned in 1922 and used as target practice by Hood, Repulse, and the rest of the Revenge-class battleships in 1925. Her Azur Lane counterpart mentions this event quite often.
USS Georgia was a Virginia-class battleship launched on October 11, 1904. She patrolled Mexican waters to protect American interests during the Mexican Revolution but was temporarily decommissioned. She was later brought out of retirement in WWI and used as a convoy ship transporting troops between the US and France. She made it to the end of the war, but she was decommissioned in 1922 after the signing of the Washington Naval Treaty and sold for scrap the next year.
SMS Roon was a Roon-class armored cruiser that launched on June 27, 1903. She served as the flagship of her group's deputy commander and was used primarily for training excercises until she was temporarily decommissioned in 1911. She was activated in 1914 and used as a scout ship in the North Sea before being transferred to the Baltic Sea to take part against Russian forces. The threat of British submarines convinced German command to withdraw older ships from the conflict and she was again decommissioned in 1916 and reverted back to a training ship. She was scrapped in 1921.
SMS Mainz was a Kolberg-class light cruiser that launched on January 23, 1909. She participated in training excercises after her launch, earning the Kaiser's Schießpreis for excellent shooting among vessels in the II Scouting Group and winning a cutter race. When WWI began she defended the German Bight before being sunk by British forces in the Battle of Heligoland Bight on August 23, 1914. Her wreckage was discovered in 2015 and can be found at 53° 58' N and 6° 42' E.