Answer to your questions.
2. That depends on amount of edits you have made, but most likely comes under traditional.
Photo of a traditional artwork still comes under traditional, some people can scan and some take pictures of their art. little bit edits like cropping, color adjustments, adding sign or watermark to the image of your artwork, touch-ups to clean the image. as long as the original art doesn't get changed drastically.
Digital is anything made using computers. but if you are making something that's started with a rough sketch traditional medias and then finished with digital, you may put it under mixed medias or even digital. .
Every category has a description. I suggest taking a walk on the submission page, going through all categories and reading their descriptions.