I played this mod a while ago and i found that i can get to the boss but when i kill it how do i respawn it back?
so i was wondering if you guys could implement the chaos type of blocks or anything that goes with the chaos dragon so i can fight it again and not trying to fight it in the end?

You don't respawn it again. You find another island. In single player, that won't be an issue. On a multiplayer server, the End is typically reset regularly. A command does exist to respawn the dragon, but it's for testing purposes only.