Minecraft – Agrarian skies – world seed

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After reading this question I understand agrarian skies modpack generates the world with nothing in it.

I recently found a world seed with multiple small biomes very close to each other, an ideal world for me.

I want to re-use this world, but start again on agrarian skies (nothing in the world, HQM totally reset, thaumcraft reset, etc.).

I have tried:

Generating a new world and traveling to the exact co-ordinates of my old world. This seems to have different biomes (due to it being a new seed).
Copying my old world and attempting to remove all player added blocks manually. (this is far too time consuming, not an ideal solution, though possible if nothing else exists).
Copying the world and removing the region directory. (this seems to generate a new seed, rather than use the old seed and generate a new world).

Is it possible to generate a new agrarian skies world from my seed so that I have a blank world with all these small biomes?

If not, is it possible to take the old agrarian skies world directory and convert it into a blank one?

Or, is there a command to remove all player added blocks?

This is on Agrarian skies multiplayer using agrarian skies v3.1.2 (I think).

I generate the world via the server startup.

Apologies for multiple questions, but I think they all relate to the same problem.

The world seed is 3922357017991451086, if it makes any difference.

I haven't used Agrarian Skies, I assume you can't just enter a world seed into the normal seed box when creating a new world?

If not, you're left with one of two options:

If you already have a world with the correct seed, then use a utility like MCEdit to bulk clear out all blocks.
If you have a world that you want to use, but it doesn't have the right seed, you can use a utility like NBTExplorer to view and edit the save file, and change the world seed.