It has been posted all your questions about IF, might be time to tell OP to pin this comment
In short
Miko v1.1 (main game, has gameplay and gallery)
IF miko v1.81 (First DLC, no gameplay just gallery)
IF miko v2.19 (Second DLC, no gameplay just gallery)
IF miko v3.xx (Third DLC, no gameplay just gallery)
Basically the reason Dev separate these DLCs is because it has become too large, so Dev decided to create a new separated game.
I don't think there is a way to combine these DLCs into one, just download each versions