The later is due to the fact that the use of only 52 or 104 cards makes it easier for the players to keep track of the cards as they are exposed. By dealing the cards face down the dealer makes it tougher for player to count cards. The use of three or more decks increases the house advantage, and players are allowed to see each other's hands to compensate for this. Should the cards be dealt face up never touch them, this restriction is aimed at preventing players from cheating. When the cards are dealt face down you are allowed to use one hand to pick them up.
Suits are irrelevant.
However, if the dealer also has a blackjack, it is a standoff, as are all ties or pushes. A winning blackjack pays the player 3 to 2. To stand means to take no more cards. The dealer plays his hand automatically. If the dealer's hand is 16 or less he must take a card.