The name of an unusual guard (almost like de la riva but reverse) and attacks

Hello dear bullies,

Yesterday at the end of the class, my instructor introduced me an awkward "guard" which he said he doesn't use a lot but I found it pretty nice, especially for the times if i get stuck on de la riva.
But even the instructor couldn't remember the name of it.

I'd really appreciate if you share your knowledge on the guards name and any attacks/sweeps you can get from there.

Let me try to explain the position:

Let's say you're in de la riva, while the opponents "right leg" is in front. (which means your left leg is inside this leg, hooking)

Then he kinda starts to open his knee to "his" right side.

Now you switch your leg, and use your right leg to get some kind of a de la riva but from inside. (i almost want to say reverse de la riva)

Now your right arm goes under your leg and from outside of his leg, pretty deep that his ankle is in your elbow. And now you bend your arm so your hand comes to inside of his leg.

Now with his hand, you try to grab his gi or belt or whatever. If these are not available, you grab your own gi to lock your hand.

So it'll end up like face is pointing to the right side (opponent's right) and you are kind of controlling his all part of his right leg under his knee.

Instructor showed me a way to take the back from here and a leg lock, but i'd be glad to explore this position more.

Any help or insight appreciated.