fake pokemon holo cards Fake cards are everywhere right

Credits are obtained by getting duplicate cards, and are used to buy any specific card

Second, you can plot your own spells

No, because since they have the same effect they are considered the same card (even if they had different names )

You usually use this to target Kiki-Jiki, which you can then use to make a copy of Resto

This is very different from, lets say, custom alter cards, as the art on those is the property of the people who make them, and also, you know you arent buying a real card. Play it safe if you print the back of an MTG card and put a custom-altered version on the front, and restrict its use to kitchen table rules

An instant or sorcery cast this way will go to its owner's graveyard