Yes, they require a background check at the time of your first application.
It does not. They WILL hire you, because the turnover rate is so high. If you get an interview, they will expect you to come in the next day, regardless of whether you have a job currently.
Yes they do. They complete it themself not clear how they proceeded
They require an online background check. It's free and you just fill in information about yourself. It takes like a day to process.