3DS games cannot be played on the DSi, nor will they be made to meet the specifications of older hardware. The only Animal Crossing game compatible with the DSi, DS Lite and DS (phat) is Animal Crossing: Wild World. New Leaf is intended for - and only for - the Nintendo 3DS, 3DS XL and 2DS.
In addition to having a small tab jutting out on the side of the card to prevent it from being used in older DS systems, it wouldn't be able to play on a DSi due to differences in the data; the DS/DS Lite/DSi all have graphics comparable to the Nintendo 64, while the 2DS/3DS/3DS XL all feature graphics comparable to the Wii and Wii U.
Yes, the 2DS is part of the '3DS family' so will play any 3DS game, such as Animal Crossing: New Leaf.
Yes.
No, it's only available on the Switch
You can change the language on the 2DS under system settings. However, depending on the region of the 2DS, some languages may be unavailable
I think you can play kirby dreamland on 2ds if preinstalled
Yes, you can buy the 2DS at Target for $129.99 (CAD/USD)
No, 3DS games only work on the 3DS and 3DS XL as well as the 2DS
Yes, the 2DS can play 3DS games but just without the 3D.
The MSRP of the 2DS as of December 2013 is $129.99 (CAD/USD)
no
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.
The 2DS weighs approximately 255 grams or 9 ounces
Yes, the Nintendo 2DS is compatible with 3DS games. However, autostereoscopic 3D will not function.