I just looked through some twitch streams at the quest mode parts and learned what I could about unlocking costumes. A lot of this is known info but some of it was new to me and hopefully someone else will appreciate it too:
You unlock costumes from getting costume parts in Quest Mode. There are a total of 96 quests mode challenges for those with an early copy of the game. Some challenges offer more costume parts than others as a reward and some challenges are more difficult while other are easy. Most, if not all, challenges seem to require that you use a specific character that the developers have already selected.
When you complete the challenge you get costume parts for a random character and costume. So, for example, on Rooflemonger's stream (
link), at about 39 minutes he does a challenge requiring that he use Jann Lee. He completes the challenge and gets rewards of 200 costume parts (200 of 1000 necessary ) for Helena, Costume 12. A DOA Encyclopedia lore entry was automatically unlocked when the quest was completed.
What I have not been able to figure out is whether Quests can be repeated for random rewards...if you just cannot do some of the more difficult quests can I go back and try and get the parts I need elsewhere?