I think it is for more memory to store in your ds lite but I am not quite sure
No
No.
No, the DS lite does not use a memory card at all.
Pokemon Emerald already works for DS Lite, all GBA games work on DS or DS Lite. (It's the bottom socket, opposite the one that takes DS games.
All ds flash cards are backward compatible so the iEdge being a DSi card will work find on DS Original and DS Lite. You just can't take a DS Lite card and put it into a DSi. You can find the genuine iEdge at repuatable vendors like dscardworld.
on a ds at the back it does NT ssay ds lite and on a ds lite it says ds lite
Yes you can. You can also connect DS lite to DS and DS Lite to DSi.
Yes, and you don't need a flash card.
Not natively, but you can get a flash card such as the R4 that will let you. Google R4 DS
Nope, the ds lite has no SD card slot so you can't use SD cards.
You can put a GBA cartridge into the Slot-2 of an original DS, or DS lite.
The original DS and DS Lite cannot take a memory card at all. The DSi takes SD memory cards.