I think Decrypt9 and the Homebrew Launcher both require an internet connection to initialize. You might be able to use FBI injection through rxTools though, which would achieve the same result as the BigBlueMenu injection.
Hold L while boot rxTools to open the rxTools menu. From there, go to advanced options. You should see an option for installing FBI. Select it. Choose sysNAND, then select check TMD only. It should tell you which TMD version you need. In the rxTools folder you downloaded, go to the Tools folder, then the fbi_injection folder. Inside there, navigate to your 3DS's region and TMD version. Take the two files inside that folder and place them on the root of your 3DS's SD card. After that, put your SD card back into your 3DS and boot rxTools again while holding L to bring up the menu again. Go back the install FBI option, choose sysNAND again, but this time choose to inject FBI. After that, you should have FBI injected over the health and safety app and should be ok to continue with the tutorial!