Q: I heard about this thing I have to pay for (Gateway, Sky3DS, etc), is that something I need?
A: No. arm9loaderhax is a superior method of loading hax that runs early in boot and opens up the opportunity for things such as true custom firmware.
Q: How do I move saves from an existing Gateway setup to device installed games?
A: See this
Q: Can I run awesome homebrew and emulators with this?
A: Yes! Custom Firmware not only enables the Homebrew Launcher, but it also will give you hacks on all versions, which means you keep it forever, even with updates.
Q: Where should I go for support?
A: For support, ask for help at Nintendo Homebrew on Discord.
Q: Can I use a 128 GB (or larger) SD card?
A: Yes, but some users have reported slowdowns when using such large sizes. Note that you cannot format the card with exFAT; you need to format it with FAT32.
Q: What about System Transfers?
A: Once you have completed the guide, you can system transfer to and from an arm9loaderhax’d 3DS or 2DS exactly like you would a regular stock console or EmuNAND (you will lose any non-legitimate games/themes/DLC in the transfer; saves will stay even for games that are lost).
Q: Help! Something bad happened and now I cannot boot…
A: Please look at the troubleshooting guide.