I’m planning to licensed my whole project under https://creativecommons.org/licenses/by-nc-sa/4.0/?ref=chooser-v1 . Is this appropriate for the jam? And would a 2D game have a chance?

And should it be brief or long?

And should it be brief or long?

Any license is fine, however projects with licenses that can be classified as open source/free-as-in-freedom will get a few extra points. Again, this is not a requirement.

Creative Commons NC (Non-Commercial) licenses are not considered free/open source by both the OSI and the FSF, however you will receive extra points if you use it but not as many as a F/L/OSS license would.

And yes, a 2-D game is fine, however it must fit the theme in one way or another.