Identify the literary element in the following lines (choose 2): "I shot him dead because-- Because he was my foe, Just so: my foe of course he was; That's clear enough; although"

The lines quoted are an example of rhyme. Here, as elsewhere in the poem, Hardy uses a simple ABAB rhyming structure. So "because" rhymes with "was," and "foe" rhymes with "although." Rhyme is used here partly to make the poem easier to recite and to remember.
The poem is written very much in the style of an old-fashioned ballad, a kind of folktale often set to music. People would come together and sing ballads at social events, such as weddings, birthday parties, and other important communal gatherings. It was important for ballads to have an easy, flowing rhythm and simple rhymes that would stick in the memory. Although Hardy's poem isn't set to music, it certainly could be, and that's because all the elements of an old-fashioned ballad are present and correct.
https://www.poetryfoundation.org/poems/44329/the-man-he-killed