No, unless you're calling someone it or that is their name. For example, Sir Henry of Yorkshire, or if they are just called sir like the football player.(It was spelled with two R's though.)
"Sir." He was knighted.
knights usually have the title of "sir" before their name.
Saint
Yes. His name did not change. The only difference before and after climbing the mountain is that he received a knighthood which entitled him to use the title "Sir" before his name.
Sir or Knight
It is capitalized when it is a title, meaning it comes before a name, but not as a pronoun, where it takes the place of a name. For example in Sir Elton John the Sir is capitalized, but in the sentence, "Hello sir," the sir would not be capitalized.
the man who make horse settle
Silver was Sir Galahad, he is the son of Sir Lancelot, who is strangely Shadow, he was given Lancelot's original name before Knighthood.
What is the gentleman's name/What is the gentleman called
You probably mean "surname". Your surname is your family name. For instance, if your name is Mike Hunt, your "surname" is Hunt.
If you mean the NFL's Carolina Panthers, his name is "Sir Purr".