1. CC can mean different licenses CC-BY or CC-BY-SA or ... https://creativecommons.org/about/cclicenses/
What is the license?
2. 3 version is compatible with the 4 version so consider to use version 4
3. You should add the license into metadata for the asset packs:
"Edit asset pack->Metadata->Release Info->License for assets" It will increase the size of audience that will be able to find your art