Actually no, the question was "that we know of". The number is CONFIRMED galaxies. That includes named and unnamed.
Because Halo has yet to actually expand beyond the Milky Way. In the Haloverse, our galaxy is what all the stuff happens in. The names you see are names of solar systems.
1. Oh there were several. Dozens, in fact. There were bi-planes, monoplanes, bombers, and even jet propelled planes! Not to mention those that were in the prototype stage.2. I'll give you two for WWI and two for WWII (one admiral and one general). For WWI, General Plumer (Herbert Plumer) and Admiral Alfred Von Tirpitz (might be misspelled). For WWII, General Douglas MacArthor and Fleet Admiral Chester J. Nimitz (you may recognize that name lol there is a class of ships named after him).
3. Hmm... This is a toughy. Not because there aren't very many, but exactly the opposite. I'll just list a couple off the top of my head that you should read up on. The C.S.S. Hunley, the U.S.S. Monitor, the U.S.S. Constitution, the HMS Victory, The Bismarck, the U.S.S. Maine, and the HMS Hood.