I agree with Eduardo Salas in 1and 2, but not in 3.
For the first part of your question: 3. Me besé a tu novia (Mi Mala by Maluma)
Translation: I kissed your gf .----------- THIS TRANSLATION IS CORRECT
For the second part of your question:
Question: Doesn't "Me bese" mean "I kissed me??" Answer: Yes, it means "I kissed me" if it appears alone.
When do you use reflexivo "Besarse"? Answer: In "Me besé a tu novia" the "me" can be omitted if we talk about grammar or sintaxis. Why it appears? To emphasize that the action "besar" actually has a special meaning for the person or in the situation. In this case, even if I don't know the song, the meaning is probably "Look, it was ME that kissed YOUR girlfriend". This use of the pronoun works with any verb, not only with "besar" and can have different meaning or intention.