Yes, it's possible.

 

Yes, it just runs them in DS mode, as is regular DS games.

 

Yes, it is possible, but for emulators I'd rather use ninjhax(if you're on 9.2 or lower).

 

or he just didn't want a gw because not easy to use and something

 

Um... The DSTwo? I mean.... "GBATemp" it's the folder name of the DSTwo....

Works fine on 3DS and you pretty much can run NES/SNES/GB/GBC/GBA/DS/ARCADEs/TOOLS/etc. (No N64, don't ask)

If you're testing an emu, I'd go DSTwo. Heck, they might even use it and you'll find lots of resources here.

Even works with modded nes games, arcade games, and you can also colorize GameBoy games and they run just fine.

I own one. I love it. There's even skin packs for it here on GBATemp. Seriously, DSTwo.

There's also a master pack of EMUs and wifi tools and savedata tools. The best part is the NDS emu pre-installed can do soft saves and even slow-mo. Just be warned, the NES emu which works has no GUI and crashes back to 3DS menu if you want to exit, but other than that, yeah... DSTwo.

Heck, looking for some glory? Know how to make a gui for DOS apps? Claim your trophy and fix the NES emu. I'd use it! Might even try to make an "exit" option so it doesn't crash back to home.