It is difficult to say whether Huck believes that the information he gives is true, as he is a complex character who often struggles with issues of morality and ethics. However, in this excerpt, Huck seems to be genuinely convinced that the information he is giving is accurate, as he has no reason to doubt the sincerity of the Duke and the King. Huck is a trusting and naive character, and he is easily swayed by those who seem to have his best interests at heart. The purpose of this excerpt is to illustrate Huck's vulnerability and his willingness to believe in others, even when they are not trustworthy. It also highlights the theme of deception and the dangers of blindly following those who claim to have all the answers.