Say you have a really nasty knot that can clearly not be undone by ordinary means. At this moment of desperation, it will definitely not work to try & pass your finger through it.
At such a moment of crisis, would it be plausible to simply cut it off, or would this some at some point undo itself?
Wet hair with warm water, and apply conditioner to the tangle. Use a very wide tooth comb or afro pick or the like. Start at the bottom, toward the ends of your hairs, and pick out the knot. Work your way up the knot. Gently squeeze the knot to help work the conditioner through and loosen the knot. It does take time, but it can be done. When the knot is gone you can rinse the conditioner out.
I wouldn't hold out any hope any knot would ever magically undo itself. Cutting out a knot involving a few hairs saves you time and work and would not be very noticeable in most locations. Once you have many hairs involved in a knot cutting is less of an option. If I had a problem like that and hadn't already accidentally ripped the knot out by overeager combing then I'd begin by looking the knot over. If you can get even a small ob ject like a needle into the lowest parts give detangling one strand at a time a try.
Elizabeth