Yes, it's possible to post it ASAP! As long as you follow the listed directions, it'll be posted to the 'Otter and Ferret 2012' AO3 collection, which mean the collection-level controls will guarantee anonymity.

In non-jargon terms:

"If I understand your directions, it'll be posted anonymously, right?"

Yes! :)

If you're logged in, you'll see the details on the story. If you're logged out, you'll see something similar to this: https://archiveofourown.org/collections/otter_and_ferret2012 ('Mystery Work' Part of Otter and Ferret 2012, etc, etc)

Let me know if you have further questions about the submission process! :D