According to 3ds.guide, it only works on FW 4.3.0, is this correct? I am a little confused about the below.
- Acekard 2i : <= 4.3.0

you will need to choose another route to install the exploit to the flashcard but you can indeed use your ak2i (once you instal the exploit on the ak2i) to hack your consoleAccording to 3ds.guide, it only works on FW 4.3.0, is this correct? I am a little confused about the below.
https://3ds.guide/flashing-ntrboot-(3ds-single-system)
- Acekard 2i : <= 4.3.0

What do I need to do more exactly? My 2ds is in 11.9To reiterate what @Lilith Valentine said, we are only talking about what you require to install ntrboot to your Acekard 2i. After it is installed to your Acekard 2i, that Acekard 2i can be used to install B9S to any 3DS, regardless of system version.
If your goal is to hack your 2DS, you should use this guide to do it:What do I need to do more exactly? My 2ds is in 11.9