Is a kiss considered Zina (fornication/adultery), and does Zina have degrees?

A kiss is not major zina (fornication/adultery); rather, it is a minor form of zina, based on the Prophet's (peace be upon him) saying: "(The sin of) zina has been decreed upon the son of Adam, and he will inevitably realize his share of it: The zina of the eyes is looking, the zina of the ears is listening, the zina of the tongue is speaking, the zina of the hand is touching, and the zina of the foot is stepping. The heart yearns and wishes, and the private parts either confirm or deny that." The true zina is the insertion of a man's penis into a woman's vagina in an unlawful manner. Homosexuality (liwat) is akin to zina, even more severe.