Since you have asked three questions, the first one is the one that I have addressed:  Find a line that illustrates Benvolio's personality.  (It is the policy of enotes that only one question can be asked at a time.)

With a name that denotes goodness in Italian, Benvolio attempts to end the street fight that begins with the insults of Abraham and Sampson and Gregory.  When the choleric Tybalt enters with his sword drawn and tells Benvolio to turn and fight, Benvolio replies with common sense,

I do but keep the peace.  Put up thy sword,

Or manage it to part these men with me. (1.1.63-64)

Towards his cousin, Romeo, Benvolio is a beneficient friend.  For, he tells Romeo when he learns that Romeo is "out of love" that he weeps at Romeo's "good heart's oppression."  He even commiserates with Romeo,

Alas that love so gentle in his view,

Should be so tyrannous and rough in proof (1.1.168)

In his efforts to cheer Romeo, Benvolio tells his cousin to look at other pretty girls in order to forget Rosalind, but Romeo is not easily swayed; he tells Benvolio pretty girls will only remind him of her that he has lost:  "Thou canst not teach me to forget" (1.1.240)  Still, the concerned Benvolio declares, "I'll pay that doctrine, or else die in debt" (1.1.241), vowing to prove Romeo wrong or die trying.  Ironically, of course, Benvolio does prove Romeo wrong, but Romeo dies trying instead despite the other good advice of Benvolio.

With a name that denotes goodness in Italian, Benvolio attempts to end the street fight that begins with the insults of Abraham and Sampson and Gregory.  When the choleric Tybalt enters with his sword drawn and tells Benvolio to turn and fight, Benvolio replies with common sense,

I do but keep the peace.  Put up thy sword,

Or manage it to part these men with me. (1.1.63-64)

Towards his cousin, Romeo, Benvolio is a beneficient friend.  For, he tells Romeo when he learns that Romeo is "out of love" that he weeps at Romeo's "good heart's oppression."  He even commiserates with Romeo,

Alas that love so gentle in his view,

Should be so tyrannous and rough in proof (1.1.168)

In his efforts to cheer Romeo, Benvolio tells his cousin to look at other pretty girls in order to forget Rosalind, but Romeo is not easily swayed; he tells Benvolio pretty girls will only remind him of her that he has lost:  "Thou canst not teach me to forget" (1.1.240)  Still, the concerned Benvolio declares, "I'll pay that doctrine, or else die in debt" (1.1.241), vowing to prove Romeo wrong or die trying.  Ironically, of course, Benvolio does prove Romeo wrong, but Romeo dies trying instead despite the other good advice of Benvolio.

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In Shakespeare's play, Romeo and Juliet, Tybalt and Benvolio are very different characters. Tybalt is a hot head. He is always looking for a fight. Mercutio refers to him as the King of the Cats, inferring that he has nine lives—perhaps that he is lucky that his poor disposition has not cost him is life. However, comparing him to a cat also infers that Tybalt is sly and sneaky, which proves to be the case when Mercutio and Tybalt fight.

Tybalt is also something of a spoiled child. At the masquerade where Romeo and Juliet meet, Tybalt recognizes Romeo's voice, and because the two families are feuding, Tybalt goes to Capulet, expecting the older man to throw Romeo out. Surprisingly, Capulet does not. Tybalt starts to have a tantrum, but Capulet cautions him:

Content thee, gentle coz, let him alone, / A bears him like a portly gentleman; / And, to say truth, Verona brags of him / To be a virtuous and well-governed youth. / I would not for the wealth of all this town / Here in my house do him disparagement.

Capulet goes on to tell Tybalt to be patient and calm down. He also says that if Tybalt honors Capulet, he will do as he asks, or he will leave the party. And so Tybalt, showing himself to be rash and uncontrollably disdainful of Romeo, leaves.

Benvolio, on the other hand, is the great peacemaker of the play. He is forever trying to keep others from fighting. Whereas Tybalt is always ready for a fight, it is Benvolio that hopes to lead others to quiet resolution. At the start of the play, Benvolio tries to stop an altercation between Capulet and Montague servants. He places himself between them, when Tybalt appears, accusing Benvolio of fighting. Benvolio denies this and tries to explain:

I do but keep peace; put up thy sword, / Or manage it to part these men with me.

Benvolio says that his is trying to break up a fight. He tells Tybalt to put his sword away or use it to break up the confrontation. Instead, Tybalt calls Benvolio a coward and attacks him; Bevolio defends himself.

By comparison, we see that Tybalt is an angry young man, always looking for a fight, while Benvolio is a young man who does his best to promote peace.