Gandalf was originally known as Gandalf the Grey. After his rebirth, he became Gandalf the White in replacement of Saruman. Gandalf the Grey and after his resurrection he became Gandalf the White.
Grey And White
Gandalf is not a horse. If you mean Shadowfax, his age is not known.
Elton John is the Wizard of the North.
The Maia itself, known to us as Gandalf, is older than the world. In the shape of Gandalf he arrived in the Grey Havens in Middle-earth about the year 1000 of the Third Age. He is killed in that form on 25th January 3019 T.A., and returns to it on 14th February. Gandalf leaves Middle-earth in autumn 3021 T.A., and from then on nothing more is known about him. So we do not reliably know how long he keeps being bound to his "Gandalf" form, or which form he chooses to generally use.As you can see, we cannot say how long "Gandalf the White" lasted beyond the 2 1/2 years before he left. Unless you mean the "Gandalf" form overall, which would then be at least a thousand years, or the actual spirit/being regardless of form, which would be older then the created world/universe.
The character Strider in The Lord Of The Rings is also known as Aragorn.
Grey And White
Gandalf is not a horse. If you mean Shadowfax, his age is not known.
He is called Gandalf most often, though Mithrandir comes up alot too.
No, Sauron is. Addendum: This is explicitly stated in Rivendell. After Frodo recovers from his shoulder wound, he is greeted as "the Lord of the Ring" by Pippin. Gandalf, who is also present, immediately rebukes Pippin for using that term and states that the only lord of the ring is Sauron. Frodo might be able to resist the power of the ring, but ultimately, he could never master the One Ring.
Gandalf was known by different names to different peoples: Gandalf to Northern men, Mithrandir to the elves and Dunedain (as in Gondor), and Tharkun to the Dwarves. Olorin was his true name as a Maia.
Bilbo Baggins
Shakuntal Devi is known as the Mathematics wizard of India.
Elton John is the Wizard of the North.
Saturn is well known for its Majestic Rings.
Spock's more well known, I'd say
Gandalf does not have a particular last or sir name. His is called by many names by different races, creeds and peoples. The most common are Gandalf the grey or white, gandalf greyhelm or Mithrandir. There may be more, but I cannot remember off the top of my head. Actually, the name is greyhame (cloak), and he is also known as Stormcrow by Rohan.
Cardinal Hall of Fame shortstop and defensive wizard Ozzie Smith was known as the Wizard of Oz.