I've seen a video of a guy working an R4i Gold 2015 on one, but what about below that? I'll be getting that MM 3DS and I'd like to know if I need to purchase a 2015 or not. I'll be sending the old 3DS to a friend once I have the new one.
I can confirm that my R4i (3DS) from r4ids.cn is working on my New 3DS XL like a charm. I didn't have to do anything at all and poof! Works! I believe I read something that Nintendo stopped blocking DS-mode carts back in FW 7.XX, but don't quote me on that one .
My N3DSXL is running the latest North American firmware with no problems at all. I've played MonHun4 and the like and yeah! R4 still works!