@BigE 1-3 is the collection of 1.5 + 2.5, 2.8, and 3, so essentially the whole series except some mobile stuff and Melody of Memory. Those others are the individual releases and within them is…
1.5 + 2.5 – This is 1, 2, Chain of Memories, and Birth by Sleep, along with the cutscenes from 358/2 Days and Coded.
2.8 – This is Dream Drop Distance plus a new side game and side story that connect to 3.
