Yes the streetpass works when a3DS game is on, but it will not work when the wireless LED is off, or when you are playing a DS game.
Streetpass is a 3DS feature.
The 3DS comes with AR (Augmented Reality) games and Face Raiders built in, along with other applications such as the 3DS camera, music player, Mii Maker and Streetpass functions.
its when you meet someone elses mii in the 3ds
Not necessarily. You can get Kid Icarus: Uprising weapon gems by streetpass even if the game is not inserted, as well as Heroes of Ruin trader data. But you would need Super Mario 3D Land or New Super Mario Bros 2 inserted to get Toad House bonuses or Coin Rush records from other people.
For getting extra options in games (like in Augumented Reality) or for StreetPass Mii Plaza for carrying on the game(s).
Some things I know are: Streetpass Mii Plaza, Super Mario 3D Land, Swapnote, and the Nintendo 3DS Sound
You need to beat and complete Find Mii twice.
The 3DS memory card is for downloaded games and their save game data. It contains your streetpass data, and you can add music to it too. Photographs and videos you take using the 3DS can be copied to the SD card also.
The 3DS' 'main' mii is used on the friends list and Letterbox for example, but you can specify a different one for the streetpass games on the Mii plaza.
heres the listings : Mii, Streetpass, 3ds Sound, 3ds Camera, AR GAMES, Face Raiders, DOWNLOAD PLAY (FOR 3DS and Ds), System Settings, Activity Log, Healthy & Safety Information, Game Notes, Friend list, Notifications and Internet Browser
No, 3DS games will only work in a 3DS.
Yes, it does. However, if you have friends on the 3DS friend list, they will be able to see you are offline. Referal via streetpass, you close the 3DS with the power still on. IF you walk past tons of people, one of these people might have a 3DS. BAM! if you walk past each other, your personal mii will go into the other person's plaza, therefore you will have a hero for find mii, person to trade puzzle pieces with, etc.