Are hatches predetermined?

I'm pretty sure the mon is determined when you get the egg, not when it hatches. I had a 10 km egg that I acquired before the babies were released, and hatched after baby release, that contained Jynx (not Smoochum). At baby release, no more Jynx's appeared in eggs, just smoochum. So almost certain that eggs are decided on when you get them, not when they hatch.

The mon is a mon when you spin it from a stop. The "egg" is just a covering that is removed after the requisite distance is achieved.

The amount of candy and stardust are determined at hatching. The Pokemon is determined at aquisition.

Yes, everything about the Pokemon is pre determined as soon as you get the egg. About a month ago I hatched a Lapras with ice shard and ice beam and ice shard is a legacy move.