You cant, its doesnt have apps like that on it yet. It only has games exclusivle for the 3DS andgames that you can download, but Nintendo doesnt have a contract with the creators of Temple Run so yourcant download it.
The 3DS does not have a game packed in with it. However, it does come with software preloaded on the system, such as: Mii Maker Mii Plaza Nintendo 3DS Music Nintendo 3DS Camera Face Raiders AR Games Internet Browser
I would recommend the 3DS XL if you don't already have the 3DS. All in all it's a personal preference. The 3DS XL comes at $30 more than the original 3DS but has, obviously, a bigger screen. Lastly, if you get the XL, get a charger. It doesn't come with it.