Are cryostar crates still farmable, or are they discontinued just like Grand Watch crates?

What event was it that deflated egg prices? Was that egg-zavier or something else?

How do I complete the "Child's Play" achievement? I know I'm supposed to defeat challeneger but who is he? What does he look like? How do I get him to spawn?

I'm a returning player; I just need a refresher.