First, we’re sometimes asked whether it’s possible to give out promo codes for paid apps, or otherwise gift apps? Answer: not at this time.
Second, if you have an app that’s certified but just waiting to go live according to your indicated release date, can you change the date so that it publishes earlier? Answer: same thing, not at this time. Another good idea for future implementation, as currently you have to resubmit the app and go through certification again.
On the subject of release dates, the documentation for this says that the date guarantees that the app won’t be released before that date (GMT time), but can’t guarantee that it will go out on that date. The latter caveat is there because the app might not have made it through certification yet; otherwise, if it’s certified, the release should happen pretty quickly. At present, it’s also not possible to set the release for a specific time.