According to Sony they do not. You can load the card right away to your Playstation account and the funds will then appear and stay in your account until you spend them.
Yeah. You just scratch off the designated area on the back and he code is revealed. Enter said code on the “redeem codes” tab in the PlayStation store and the money will be put into your online wallet.
Only the ones that say they are a digital download. Physical cards need to be mailed to you and/or picked up at a store. Check the other denominations for digital download options.
Yeah, you will get an email saying that "Funds have been added to you wallet". And the amount will show in the top right corner of the PlayStation Store.
Yes, it'll ask you for the payment method at point of purchase which is where you'll choose the PlayStation Store Card and enter the code on the card. Hope this helps.
I don't know if Best Buy is an international store but buying these cards in the US most likely are US cards. I know the Hong Kong and Australian cards look different and denote their country's denomination so I don't think you could possibly buy one for a different region.