Can you bet both ways on the same stock or index?

Yes, you can bet both ways on the same stock or index, with trailing stops on both (IG spread betting and some others have a ‘force open’ button that ensures the second opposing bet doesn’t close the first). I have attempted it, successfully and unsuccessfully (unsuccessful when price twitches both ways quickly enough to take out both stops creating two losses!). It is quite tricky finding sensible distances for the stops and balancing them with potential gain – pushing stops further away might sound obvious but only if the available gain is worth whichever loss gets booked; placing the stops closer can mean more easily hitting both.