The first thing I must point out is that this question is actually a trick question, and at first glance even I almost didn't realize it.
The correct answers here are L Morte d' Arthur and Beowulf and I will explain why:
Now to begin, most of these poems are considered to be epic poems. All except "The Decameron" have a classification of being epic poems, but there is one poem that stands out.
In the medieval period, many authors used the technique called the “framed narrative”. A framed narrative is a story (or multiple stories) within an overarching story and some examples include Geoffrey Chaucer's "The Canterbury Tales", Giovanni Boccaccio's "The Decameron", and Dante Alighieri utilized it in The Divine Comedy.
The Divine Comedy is a epic poem, but it is unique and not written like traditional epic poems. Thus it is more-so a Framed Narrative more than a early epic poem.
Next, we must look at when these poems were written even though we already have our answer:
Le Morte d' Arthur:
Beowulf:
The Decameron:
The Divine Comedy:
I'll be back to edit in abit ok?