How we cite our quotes: (Canto.Stanza)
Quote #4
In her first passion Woman loves her lover,
In all the others all she loves is Love,
Which grows a habit she can ne'er get over,
And fits her loosely—like an easy glove (3.3)
Byron suggests that the first time a woman has sex, she is totally in love with the person she's having sex with. From that point on though, the woman loves the idea of being in love more than whatever specific man she's with. Patronizing much, Byron?
Quote #5
The favour of the Empress was agreeable;
And though the duty waxed a little hard,
Young people at his time of life should be able
To come off handsomely in that regard. (10.22)
Earmuffs, all you youngsters out there. Byron's use of the word "hard" here could humorously refer to Don Juan's erection. On top of that, Byron jokingly suggests that the best way for a young man to make money with an Empress is to turn himself into a prostitute.
Quote #6
One monstrous diamond […]
Bestowed upon him, as the public learned;
And, to say truth, it had been fairly earned (11.39)
Byron hints that Don Juan has earned an expensive gift from Catherine the Great by being a sort of sex servant to her. He never confirms this one way or the other, but that's exactly what makes it so titillating.