Knowing the SQL commands to achieve this is a useful lore for the community, but the easiest way to bypass registration on a Kobo e-ink device is to copy over a database with a blank, (or fake) User. You are welcome to use the one I created for this purpose:
http://www.transfer.sh/1C1MipV/KoboReader.sqlite
Connect the Kobo to a computer via usb, and replace the existing file in the .kobo directory. (it might be in a sub, directory.) Eject your device, and restart it.
I'm not really advocating you do this. Disadvantages include: No longer any syncing, which also means no updates to firmware without manually updating it yourself. Also, the Kobo will not be able to download any new dictionaries. If the pre-installed dictionaries are not all the ones you want, or get deleted, (very easy to do by accident.), you have to manually download and install them yourself.
It should be obvious, but this also means the kobo will only be able to use e-books with no drm.. Whether they are purchased that way, 'found' that way, or made that way yourself, is an exercise for the reader.
The advantages, if you go down this path,, once you have the files you want, you can bootstrap your kobo, (or any other kobo) any time you want without the hassle of connecting to wifi and filling out the registration form.