1. emuNAND is only available on GateWay for 3DS v4.X. (Not including redNAND)
2. If your 3DS is on v6.2 and you never made a NAND backup when it was in v4.X, then you can't flash back to v4.X.
3. No, you can't use someone else's NAND backup to downgrade as it won't work.
4. The K3DS, Sky3DS, R5SDHC are both exactly the same. They work on the latest v9.X firmware, but also have many limitations.
2. If your 3DS is on v6.2 and you never made a NAND backup when it was in v4.X, then you can't flash back to v4.X.
3. No, you can't use someone else's NAND backup to downgrade as it won't work.
4. The K3DS, Sky3DS, R5SDHC are both exactly the same. They work on the latest v9.X firmware, but also have many limitations.
- They're a 1:1 copy of a 3DS cartridge.
- 10 Game limit. (From what I read)
- Can only switch games with a press of a button. Takes about 6 seconds to switch.
- No region unlocking. (If you have a US 3DS with K3DS, you can only play US 3DS roms.)
- Quite possibly very easy to be blocked by Nintendo once they come out since Nintendo can just send out an update and block them.
- Can't use homebrew.
- Can't use modified roms (I found someone who partially undubbed a game, but only works with GateWay.)
- Can't install .cia (DLC+eShop games)
- Almost twice as expensive as Gateway.