[NSFW] Full nelson and frontbend tags

I have a little question! What is the difference between the full nelson and frontbend tags?
At first I thought depending on whether sex is happening or not, but it is used in both cases.
If there is no difference, then can we combine them into full nelson?

full nelson is when they’re being held up by the partner, frontbend is when they’re in the legs-up pose all on their own.

Now, I’m not quite sure the difference between full nelson and reverse suspended congress - I guess the legs don’t have to be straight in the latter?

The reverse suspended congress differs from the full nelson in that in the reverse suspended congress:

In the full nelson: