I need a little help

So, I am working on a mod where killing the Ender dragon acts like killing the wall of flesh in terraria, so I would like some coding advice on how can I detect that the ender dragon is killed, and after that:

-Grant a custom achievement (to all players)

-spawn ores, (maybe structures too)

-enable certain custom entity spawns (normally they don't spawn before killing the ender dragon, so for example stronger variants of base mobs)

-enabling a new loot pool that drops loot from entities, that normally would be unobtainable before ender dragon