First part means that if you have opened a BUY trade in EURUSD your trading software will not allow you to open a SELL trade in EURUSD while the buy order is open.
FIFO means that the open trades have to close in chronological order so if you have placed 4 BUY trades in EURUSD (trades 1, 2, 3, 4) then you will have to close them in the same order, 1, 2 ,3, 4. you cannot close trades 2 3 or 4 before trade 1
If your trading software has a CLOSE ALL function , it will close them in FIFO order .
These are silly rules in my opinion and one day they will probably be removed.
I don't know what purpose they serve, it seems to me that they are only there for to give 1 more edge to the brokers (as if they haven't got enough edges....)
Thanks for the explanation. Very well explained. What world of unthoughtful programmers do you live in? IBKR allows you to put through any order any time anyhow you want. They just execute when they match.
You said "hedging" so I got interested. IBKR also has a hedge feature but really you can do that same thing by adding another order so it's really useless and aesthetic. You can do it faster using their API than selecting with mouse clicks anyway. But what got me interested was that your said hedging was banned. What does that mean? How can anyone stop you from hedging? Hedging being buy one thing and another thing to lower your risk.