Hi there! For the image reference, you can use random image generated from character creator / use images found from Google for hairstyle / outfit idea. There isn't really any requirement for the level of detail, you can give as much detail as you want / can provide :)
For the interview, there's no need for you to give the voice. I usually only ask for you to specify the rough personality for the character you design and write dialogues based on that set personality.
Hope that helps!