As for any other card game, from time to time, judges will deck check certain players at the beginning of a round.
Tournament officials will be able to quickly perform deck checks with the Altered app by scanning all of the QR codes in the physical deck.
A deck check only verifies whether your physical deck matches the decklist you registered for the event. You’ll always be able to play with any version of a physical copy as long as you have any version of those cards in your collection/registered decklist.