First of all, Burns’s poem is not fourteen lines. Burns is a Scottish lyric poet. I think his metrical forms are mostly borrowed from Scottish folk songs, and there are not many standard metrical styles.
The fourteen-line orthodox Ruyi style (Petrarchan style) is 4433, and the British style (Shakespeare style) is 4442, but there are many variations, including segments such as 446 and 86. The rhyme pattern of the fourteen lines is generally Bao rhyme (abba) in the Italian style, and abab in the English style.
This poem is a four-line poem with interlaced rhymes. The number of steps in each line is not uniform. It belongs to the folk style and is not a metrical poem, let alone a fourteenth line.