not it has not yet happened. the hard fork is apparently scheduled to happen on November 1. what is already over is the block that they used as their reference for distributing the BTG coins.
you can already see what the bitcoin price is!
and you can also see the BTG price which is very different in different exchanges. i have not checked bitfinex yet but in yobit it was 0.08BTC=456$
If that is correct that seems like a great opportunity to do some arbitrage between the exchanges, unfortunately Im not into that kind of thing so I wont be able to take advantage of that opportunity but Im sure there are any people in the forum that could do it if they have the right tools and knowledge.
the coin is not released yet. these exchanges only gave their users some promised fake tokens which will only work on their platforms so that you can trade them.
in other words there is no blockchain available for you to buy at one place then transfer the tokens using the BTG network to other exchange to sell. that is why the difference exists!