How trading will work in Pokémon TCG Pocket: Requirements and limitations for trading repeat cards
Regarding the cards that can be modified, it is confirmed for the moment that all basic cards will be available for modification, i.e. between levels 1 and 4 diamonds. This includes the original Ex cards. Among the “rarer” cards, only level 1 Star cards, i.e. the most basic cards of the rank, can be exchanged.