[Blackjack] Which cards of the dealer do i get to see ?

In a normal black jack game i get to see the dealer's cards after each hand, and so i can know better of the next cards up.
but here, there is no function that tells u which cards the dealer had, and so I can't use this information .....
or can i ?
is there a way to tell the deck's content after each round ?

You can, when the status is "HANDOVER", the dealer's cards are revealed.

Thanks, so just so i get it straight -
I can use all info that the functions returns, but i cant use global vars like $__gamestate["cards"] ?

Yup, you can (and should) use everything the functions return. You absolutely should not access any of the library's global variables (they'll be different anyway, but it will still get you disqualified ).

During the game the dealer has an up card and a down card. Is the up card revealed before status "HANDOVER"

You should read the rules. Yes, the up card is always visible, the down card is removed from the deck, but is not visible, and when a hand is over, all the dealer's cards are revealed. If the dealer gets a blackjack, his cards are immediately revealed as you need to place a new bet.