Bandai says that it was released in September 1996 (It was also said that there was no exact release date left.) In summary The answer of title, Pokemon cards printed earliest is the Pokemon card released before Sep 1996
The remaining eighty cards are all Unlimited
Local Collectibles Stores If you search sell Pokmon cards near me on Google, youll likely see a list of collectibles stores near you
For example, you can't cast a creature card with mayhem you couldn't normally cast during an opponent's turn, even if you discard that card during an opponent's turn
You can mix and match, for example grab two from the Phyrexia: All Will Be One set and grab two from the Dominaria United set to battle against each other
It might be a touch less good if you know you have to wait until turn 4 to cast your Jetmir, Nexus of Revels, but I think youll catch up