All DS games now rely on the DS clock, starting from Animal Crossing: WW. So no, they have no internal batteries as far as I'm aware.
Also, the only special thing about foreign ones are the names, I guess. They're completely normal and unremarkable otherwise.
Uhh....
I got a Aipom named Capumain or something....
Is that Aipom in a dif language....?
How do I stock Pokemon to Pal Park?
Its among the flowers on the left side ledge of the big hole in the middle where you battled the galactic grunt