There are no 'hidden charges' on the DSi. You can buy some games from the Nintendo DSi Shop, which cost money, but that's optional.
The Nintendo Dsi costs around £149.If you just want to play games on it you ight consider a Nintendo ds lite which cost around £99.The only difference i know of is that Dsi's have a camera and a few other settings.
No.
yes, $169.99
It truly depends on if you want to upgrade to the new Nintendo system. The Nintendo 3DS is the currenty generation for Nintendo games and DS support including internet gaming are not in use anymore. It will cost you money but if you want the newer selection of games that are only avaible on the Nintendo 3DS, it would be a good choice to get it. However, the Nintendo DS already has a wide selection of games, so if you think that those games are enough, then it is uneccesary to upgrade.
If you get a used Nintendo 3DS, it will cost about $79.99 at GameStop. A new Nintendo 3DS will cost just under $150. The games themselves are relatively cheap compared to an Xbox.
Any where from $0.50 to $75.00
It should be backwards compatible with all DS and DSi games. However there are a few things that can't be supported:Games which require the Slot-2, such as some Guitar Hero games (with the controller)Playing online on a network protected by WPA (old DS games only) won't usually work.The DSi won't support them either, but it's not much of a problem.
no, its free on the dsi shop
You can download it from the Nintendo Eshop (may cost money)
about 100 to 200
Rs.6400