Alright, thanks to zoogie and
his tool, we may found a way to install FBI on a 2DS (It's also useful for O3DS if you don't want to do the whole cfw process) :
Works up to 9.8 (emunand) for EU and JP consoles :
Works up to 8.1 for US consoles :
Download this pack :
http://jheberg.net/captcha/fbi-injection-13/
1. Use the gateway launcher.dat to create your emunand (format emunand, backup your sd card content first
2. Setup rxTools :
http://www.rxtools.net/#!howto (replace the rxTools.dat with one of the patched one). If you have an EU or JP console, update your emunand now.
3. Use rxTools to get your nand xorpad (Decryption Options -> Generate fat16 Xorpad). Put it on the FBI injection folder
4. Open emunand tool, choose extract emunand then choose the FBI injection folder for the destination
5. Execute decrypt.bat
6. Open WinImage.
7. Drag and drop the emuNAND.fat16.bin on the program then click on OK
8. Go to title/0040010/00022300/content for a EU console, title/0040010/00021300/content for a US one, and title/0040010/00020300/content for a JP one.
9. For EU and JP consoles :
- Delete the *.app and the *.tmp from the content folder.
- Click on Image->Inject then choose the *.app in the content_region folder.
- Same process for the *.tmd file
For US consoles :
- Go to the content_US folder
- If needed, rename the *.app to match the one in the title/0040010/00021300/content folder
- Delete the *.app from the content folder. (in WinImage)
- Click on Image->Inject then choose the *.app in the content_USA folder.
10. Save and close WinImage.
11. Execute reencrypt.bat
12. Restore your emunand with emunand tool.
13. Boot on the emunand with rxTools. Select Health & Safety app. FBI should boot instead.
14. If you have an US console, install another CIA installer from it (because the update will restore the original Health & Safety app) then update your emunand.
Tested it on a 4.2 O3DS and it works fine, so it should work on a 2DS too.
A big thanks to
@zoogie for the original method and
@Riku for making it work on 9.0-9.8 (emunand) on JP and EU consoles.