>>103149841) no, but duplicate cards are needed for ranking up to the highest possible card ranking. To rank up an S card to R you need another S card of the same kind and theme. So they're worth saving if you intend to do so
2) Through special card packs, in the shop there's a few from 2018. 2017 and 2016. And those cost diamonds.
3) I tried doing one of those surveys but didn't get anything from it
