The ABAB or ABBA refers to the song's rhyme scheme: ABAB means that the 1st and 3rd lines rhyme with each other and the 2nd and 4th lines rhyme with each other. ABBA would have the 1st and 4th as one rhyme and the 2nd and 3rd as another.

I assume the octosyllabic term refers to 8 syllables per line.

4/4 time would have 4 beats per measure (bar) and each beat would be represented on the sheet music by a quarter note. Guantanamera fits a 4/4 time signature.

Hope this helps.

Jeff