Yes, the graphics are the same, just without the 3D feature.
Yes, the 2DS can play 3DS games but just without the 3D.
Yes, the 2DS can play 3DS games as well as DS and DSi games.
Yes, the 2DS can play 3DS games as well as DS and DSi games.
Yes, the Nintendo 2DS is compatible with 3DS games. However, autostereoscopic 3D will not function.
Yes. The Nintendo 2DS is built to play 3DS games, so the mini cartridges are the same as those used on the 3DS. The 2DS does not have its own library of games separate from the 3DS.
Yes, Pokémon Omega Ruby and Pokémon Alpha Sapphire are 3DS games and therefore they're available to be played on any of the Nintendo 3DS or Nintendo 2DS systems that can play 3DS games and that includes Nintendo 3DS, Nintendo 3DS XL, Nintendo 2DS, the New Nintendo 3DS and the New Nintendo 3DS XL.
Yes, any charger that fits a DSi can be used to charge a 3DS, 2DS or New 3DS, they all use the same charger.
Yes, you can. There is a headphone jack for the 3DS and 2DS as well.
Yes, the 3DS can be used to watch YouTube videos. However, the YouTube app needs to be downloaded first from the Nintendo eShop (at no cost).
No, 3DS games only work on the 3DS and 3DS XL as well as the 2DS
As of October 2013, only the 2DS has been announced
Yes, the Nintendo 3DS can play DS games as well as 3DS games in 2D