In the casino, 777 is often associated with slot machines. When three 7s line up on a slot machine's payline, it traditionally signifies a jackpot win. This combination is considered lucky and is often associated with big wins and good fortune in gambling.
Yes, you can play for, and win, real money when playing blackjack on mobile devices. It works in exactly the same way as it would on a desktop online casino, and the same real money prizes are up for grabs too.