Alright, so here we go:
As far as being worldwide, I'm not entirely sure if it's globally accepted or not.
However, I can vouch for the fact that:
1) It does accept Paypal, so you're money transfers to and from are instant.
2) It is definitely legit. I've deposited/withdrawn money from it several times over the past couple of years. There is a delay when you first get started. It's part of their built-in fraud/liability protection, but once you make an initial investment, I believe there is a waiting period (like a week or so) before you can withdraw it again. That's ONLY when you start your account though. After that you're good.
And yeah, to answer the last question, you can initiate a sell on Stock A, but keep in mind if you sell on a weekend, or after hours during the week, the sell WILL NOT GO THROUGH until the market opens again. You should however get the value at the time of sale though, so you won't lose any money if, say, you sell on a Saturday at 3:30PM and the stock bombs by Monday. They just make you wait til the market opens to see it
