Yes, you can download demos for free.
Also, if you qualify for the ambassador program, you can get a few free GBA games
You'd look on the DSi shop or the 3DS eStore, and look for any games marked 'free', then just download them to the console.
any ds or 3ds game can be played on any 3ds system.
3DS's are not free from a retail shop. Here are the colours available (From date of release): Aqua Blue Cosmos Black Flame Red Pearl Pink Ice White Cobalt Blue Midnight Purple
Various applications and games such as: Mii Maker, Mii plaza, AR games, Face Raiders, N3DS Camera, Nintendo e-shop, Settings, and any other games or apps you download from the e-shop.
The 3DS doesn't currently come with any preoloaded points for the DSi ware shop.
yes
No
It can play European DS games, but not European 3DS games. 3DS games are region locked, but you can still play regular DS games on any 3DS console (tested with European 3DS and US DS games).
Regular DS games from the UK will work on a 3DS from any region, including the US. It is only the 3DS games that are region locked, so a UK 3DS game would not work.
The 3DS has its own library of games, but can also play any games released on the DS or DSi.
3DS games are region locked, a 'French' one (actually an EU one) will work on any European 3DS, and also the Australian one.
No, a licensed NDS game should not affect the 3DS is any way because the 3DS is backwards compatible and can play NDS games