Look at the back of the cartridge - on the PCB there should be a number or letter on the right which tells you the revision. If yours is listed in one of the flash backups, then it's possible to restore. You will need ntrboot-flasher to restore the flashcart back to its working state.
- Copy the (.bin) backup from the folder containing your flashcart's revision (the wrong revision will not work), create a folder onto the root of your console's SD card called "ntrboot" and paste it inside of the folder.
- Inside of the "ntrboot" folder, rename the flash backup (.bin) file to "R4iGold3DS-backup.bin".
- Make sure you create a text document and rename it to "ntrboot.log" as otherwise ntrboot-flasher would think that you haven't backed up the cart yet.
- Download the "ntrboot_flasher" FIRM file (https://github.com/ntrteam/ntrboot_flasher/releases/latest) and copy it into the "luma/payloads" path on your console's SD card.
- Power on your 3DS whilst holding START, and select the "ntrboot_flasher" option from the chainloader menu.
- Select the 'R4i Gold 3DS' option, and select 'Restore Flash'.
If both of these steps were successful, then you can fully use it as a flashcart again.
Also, what's the max microSD size I can put in here?
32GB microSDHC max, but larger capacity cards will work. It must be formatted to FAT32 only, it will not work if it was formatted to exFAT or NTFS filesystem.
What's the latest firmware I can put on the cart?
Firmware is different from the kernel. The kernel is the operating system, that is, the games menu you see when you start the flashcart which is loaded from the microSD. The firmware is what makes the flashcart tick (i.e., tricks the DS into thinking that it's a retail game).
The latest kernel can be found here:
https://sanrax.github.io/flashcart-guides/cart-guides/r4ids_cn/
