I heard that I can request to put my app in a holding area when I submit the app – meaning that, the app will get reviewed but not made publicly available until a later day (and that date is undetermined at the time of the submission, for example we probably would like to have some major marketing event planned for the app etc).
Is that true? If true, will that delay the review, since the lack of urgency?
When first submitting an app to iTunes Connect, you can set a release date in the future. This will prevent your app from going live as soon as it is approved.
When submitting updates, you’re asked whether you prefer to release the update yourself or let it go live as soon as it is approved.
I have never seen this influencing in any way the review process. I believe that (generally) apps are processed in whatever order they are submitted.
Note that the release date can be changed anytime after the review process; as well as the countries you’re releasing your app to.
In the opposite case (you don’t want to delay your app release, but rather accelerate it) you can ask for an “Expedited App Review”, which might be granted if you have valid reasons to back your request:
Apple: Request an Expedited App Review
Some say that setting the release date after the approval date can affect your position in the “newest apps” list on the iTunes Store. I have no reliable data that either denies or confirms this scenario.