Do not ask if you can achieve this without a hardmod, you can't.
This is an apparently working implementation of the "FIRM partitions known-plaintext" exploit detailed here. Reports of successful downgrades are sparse or unconfirmed, but seeing as anyone who tries this has a hardmod and a NAND backup (hopefully multiple backups kept in multiple locations), there isn't really much that can go wrong.
This should work on both a New and Old 3DS.
Keep in mind throughout this that 10.4 and 10.5 use the same NATIVE_FIRM. Also keep in mind that 10.3 does not have a unique NATIVE_FIRM, and we will be using the 10.2 NATIVE_FIRM.
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What you need:
- Your 10.4 or 10.5 NAND extracted using your hardmod
- Raugo's autofirm pack (Mirror)
- msvcr120d.dll (Mirror)
- The appropriate decrypted NATIVE_FIRM CIAs which can be found on my Github page.
Instructions
1. Extract the autofirm pack to a folder of your choice
2. Place a copy of your NAND file (named "nand.bin") in the autofirm folder
3. Download the appropriate decrypted 10.4/10.5 NATIVE_FIRM and the decrypted 10.2 NATIVE_FIRM as CIA files
4. Rename the 10.4/10.5 NATIVE_FIRM file to "firmoriginal.cia" then put it in the autofirm folder
5. Rename the 10.2 NATIVE_FIRM file to "firmnuevo.cia" then put it in the autofirm folder
6. Place the msvcr120d.dll file in the autofirm folder
7. Run "start.bat"
8. If everything worked, then you will have a modified "nand.bin" containing 10.2 NATIVE_FIRM on 10.4/10.5
9. Flash this "nand.bin"
10. Get access to the homebrew channel (Starter kit here) (Mirror)
11. Downgrade to 9.2 (Mirror)
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Please reply with your bugs/issues or with confirmation of a successful downgrade
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Thanks to @swarzesherz and @ceapr for their 3DSFat16tool, /u/StillUsesWindowsXP for his homebrew guide, @Raugo for his autofirm tool, and to the #3dshacks@rizon IRC channel for the 9.2 downgrade guide.
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Confirmed Successful Downgrades:
/u/minkintn (#3dshacks@rizon), [o3DS - 10.5U -> 10.2U -> 9.2U]
@vb_encryption_vb (gbatemp), [o3DS - 10.5U -> 10.2U -> 9.2U]
@thaikhoa (gbatemp), [n3DS - 10.5E -> 10.2E -> 9.2E]
@Dean_ (gbatemp), [o3DS - 10.5E -> 10.2E -> 9.2E]
@Spore2 (gbatemp), [1.1.0U -> 10.5U -> 10.2U -> 9.2U]
@shadowofdarkness (gbatemp), [9.2U -> 10.5U -> 10.2U -> 9.2U]
@DigitalJosee (gbatemp), [10.5 -> 10.2 -> 9.2]
@mvmiranda (gbatemp), [10.5U -> 10.2U -> 9.2U]
@simon66 (gbatemp), [10.5U -> 10.2U -> 9.2U]
@boyjkp (gbatemp), [n3DS - 10.4U -> 10.2U -> 9.2U]
@mitroux (gbatemp), [o3DS - 10.5 -> 10.2 -> 9.2]
@Ninje (gbatemp), [o3DS - 10.5 -> 10.2 -> 9.2]
@laguillo (gbatemp), [o3DS - 10.5J -> 10.2J -> 9.2J]
@KipMudz (gbatemp), [o3DS - 10.5U -> 10.2U -> 9.2U]
@hojjat_modder (gbatemp), [o3DS - 10.5U -> 10.2U -> 9.2U]
@Plasma Shadow (gbatemp), [o3DS - 10.5E -> 10.2E -> 9.2E]
@hundshamer (gbatemp), [n3DS - 9.0 -> 10.5 -> 10.2 -> 9.2]
