I have two questions about the rules (I’m NOT asking if the cards in the pic are legit)

I bought a box with three full decks and tutorials to teach new players how to play, these in the picture are two of the cards from one of those decks. As you can see, they have a little shape and a number in the bottom right, used in the tutorial. My first question is: does this mean I can't use these cards in a regular deck? If I were to enter an official tournament, would these cards be allowed?

Most of my cards are in Italian, but I have a few in English and other languages. Is a deck supposed to only contain cards in one language, or can I mix them? When I was a kid we believed a myth according to which all non-italian cards were supposedly fake, so I couldn't play them, but I know that's not true lol. However the manual doesn't state whether the language of the cards matters, so I'd be grateful if you could clarify that to me