Yes, you can leave your suit jacket unbuttoned when standing and for sure unbuttoned when sitting, depending on the style and fit of the jacket. Leaving it unbuttoned allows for more freedom of movement and a relaxed appearance.
As a general rule of formal wear etiquette, a jacket should be buttoned when standing and unbuttoned when seated. Of course, there are additional rules too. On a two-button jacket, only use the top one when it's time to button up.
Online Blackjack Uses Continuous Shuffle Machines\n\n This makes dealing easier for the house and also reduces players from having success counting cards. The CSM is capable of shuffling the cards much more effectively than a dealer can. If you want to card count, it is advised to find a traditional dealer shoe.
Remember: you can play online real money blackjack with a bonus on all of the sites on the list above. Many games are available in demo mode, and you can (or should) keep playing new ones until you find your favorite variation of the game. Getting the basics right helps you to try and defy the house edge and win.