1. Download the latest version of Gateway from the gateway site
2. Download the downgrade package from gateway site for your region (DO NOT USE ANOTHER REGION OR YOUR 3DS WILL BE BRICKED!)
3. copy Launcher.dat and the downgrade file you've downloaded to your SD card
4. open brower on 3DS and go to go.gateway-3ds.com (if it doesn't work clear cookies and browser history and try again)
5. Go all the way to the right in the menu using the d-pad and select downgrade with the A button
6. Follow on screen instructions
You do not require the gateway card for this to work!
When on 4.5:
1. Boot CN
2. In the main menu press L+R+X+Y
3. Choose yes and then yes again to remove the save (and the exploit)
4. Reinstall the exploit now for 4.5
If you want to be on 9.x for the new encryption (handy if you want to use new titles with Pasta) just search around and find a tutorial on how to update to 9.2 using Pasta.
Would it be safer to upgrade via another cart rather than downgrade and then come back up? What versions are confirmed functional? I thought mine would be as it's described as working from 4.x all the way up to... 9.2, but if that's not the case, which ones DO work? It wouldn't be a big thing to go snag a used copy of like... Spongebob Heropants and upgrade to 8.1.0, provided that version works.
In other news, I appreciate your time in answering my questions!
The browser WILL NOT be updated with using a game cart. The problem is not your system version (8.0) but the fact that the -10 means you have a browser that is from an older version (4.x). Smea hasn't made the exploit work with that specific combination and thus you'll have to first downgrade then upgrade using pasta (which will update the browser as well), and then reinstall ninjhax again to get it working on a 5.x or higher firmware (9.2 would be recommended as it's the latest version that is exploitable)