If you use dark hole and your opponent has van guard of the dragon face down def mode does effect still work after resolves?

It's a little tricky to answer this question directly because you're mixing up terms from different card games. It seems you're trying to combine elements from Yu-Gi-Oh! and Magic: The Gathering.

Let's break down why this isn't a straightforward scenario:

* Dark Hole is a card from Yu-Gi-Oh!

* Van Guard is a term from Cardfight!! Vanguard.

* Dragon Face Down Def Mode is a combination of terminology that is not standard in any of the above card games.

Here's how we can make sense of your question, assuming you're asking about Yu-Gi-Oh!:

In Yu-Gi-Oh!, Dark Hole is a spell card that destroys all monsters on the field.

In this scenario, Dark Hole's effect would still work even if your opponent has a monster face-down in Defense Position. The effect of Dark Hole doesn't care about a monster's position or attributes.

Here's why your question is a bit confusing:

* "Vanguard" in Yu-Gi-Oh! refers to a specific type of monster (often a boss monster) but doesn't necessarily mean it's face-down in Defense Position.

* "Dragon Face Down Def Mode" is not a standard term. In Yu-Gi-Oh!, monsters can be face-down in Defense Position, but we don't use "Dragon" to specify a monster type in this way.

To clarify, if your opponent has a face-down monster in Defense Position and you activate Dark Hole, that monster will be destroyed along with any other monsters on the field.

Let me know if you have any further questions about Yu-Gi-Oh! or other card games!