In the context of ancient Indian history and literature, only two pairs from the provided list are correctly matched: Pair 1 and Pair 2.

1. Devichandragupta is indeed authored by Bilhana, a notable Sanskrit poet of the 11th century.
2. Hammira-Mahakavya is attributed to Nayachandra Suri, a poet from the 12th century.

However, Milinda-panha is incorrectly matched with Nagarjuna; it is actually attributed to a later Theravada tradition and not directly linked to Nagarjuna, who was a prominent philosopher in Buddhism. Lastly, Nitivakyamrita is authored by Brahmanand and not Somadeva Suri, who is known for his works in narrative poetry, particularly Kathasaritsagara. This analysis aligns with standard UPSC-level sources, which emphasize the importance of examining authorship in the context of historical texts.