I can at least help with the first question.
What they mean by that is how you acquired each part of your costume. Like, did you make it, buy it at a store, have it commissioned, etc. Pretty much what this is for is if you didn't make the majority of the costume yourself, it won't be submitted into the Costume judging aspect and will just be judged on performance.
However, if, say your friend, mom, grandma, whoever made the costume, didn't get paid for it, and is attending the con (have to have a badge) then the costume can still be entered in the costume judging part. Just, if it wins, the creator of the costume will win instead of the person wearing it.
I think I explained that well enough.
Let's tackle the 2nd question as well...
As far as I can tell, what this is asking, is pretty much everything that's happening during your skit. If you want certain lighting somewhere on the stage, on a certain person, etc, to list it. Let them know what sound effects/music you'll need and when during the skit. Accessories, pretty much anything you need on stage other than yourself/your prop weapons. Script is pretty straightforward, I assume they'll just want a copy of the script.