If a single is on the "production" tab and you're working on the checklist items for "lyrics," "song," "choreo," and "marketing," you need to drag the studio into the office of the person who will work on that item.
For example, in this screenshot:
Looking at the second single, "Give Me All You Got," we need to finish the choreography in order for the single to be ready to release. Dance choreography is done in the dance studio by the dance coach. In this screenshot, I've clicked down on the single's card in the production tab and started to drag it; notice how in the building view, the dance studio is lit up, with the text "Choreography: 27" popping up to indicate that if I drag my single into the dance studio, that task will be done by a staffer with that rating.
For each task, clicking on the card and starting to drag it will cause relevant rooms to light up with the relevant info. Once you've completed every item on the checklist, the green "release" button on the single card will light up.
I think this addresses the part that you seem to be having trouble with, but if this explanation doesn't answer your question, it might help if you post a screenshot of the part that you find yourself getting stuck with.
To answer your other question, dating will be added in a future update (including content that was part of our first Kickstarter stretch goal).