You just need to download the English menu folder and override your current language file with an English language file.
http://www.modpiiri.com/asennusohjeet/dstt/dstt117.zip TTDS English v.1.17 MENU
If you want to play gba games on a ttds then you need a gba emulator compatible for the ttds but i don't think there is one.
Yes.
ds hobro
nope
You can get them off the internet, just search buy ttds. Also it depends where you live but there might be some shops around that sell them
go to amazon.com
Yes, TTDS / R4DS are illegal, but ONLY if you use them for "ROM"s. You can apparently use them for other kinds of media, like music.
No they can not go into dsi XL or dsi. There is a possibility that the system will break. But there is a dsi or dsi XL TTDS like chips.
yes it will work with any ttds any game that contains Pokemon except the game boy versions of Pokemon will not work
Nope, not if u get the stupid update in DSi shop