If you’re pressing a button and want to cancel you can pretty much universally just move off the button before releasing the press and it won’t trigger the action. Works 99% of the time with a mouse, almost as often with a touch interface. Some custom-coded buttons will action on start press (not great imo) and some buttons do some other action on a long press, but if you’re holding it and nothing else has happened just dragging off is safe enough.
This didn’t sound right to me, I’m sure I heard LGBT more than 15 years ago, so I looked it up. According to Wikipedia LGBT was first used around 1988 but OED says 1992, other sources say it became widespread in either the 90s or 00s (varies by source). So 15 is a lower bound for widespread usage but I don’t think we can get much more specific than “15 to 35 years ago”.