Individual iOS Developer and other people's resources

As Individual Developer for iOS can I use other people’s resources (soundtrack, asset store plugins and artwork)
or will that violate iOS Developer Program ?
Can I hire other people, to do graphic for example ?

As long as the resources are acquired legally and you adhere to whatever licenses they have, that’s fine.

You are legal to use others’ resources in your own game:

  1. If you get authors’ permission
  2. If author indicate the content is free to be used by anyone. (including commercial purposes)

Other than that, it’s considered plagiarism in theory.

Of course, you can and should hire artist to create resources for your game.