The blue card requires FW 4.5 which is undoable on n3ds you're out of options and to be quite frank its pointless.
The op has his solution but yes the r4ids.cn card work on the n3ds. I have 3 working just fine on 9.0.I do believe the R4i Gold DS flashcart is still compatible with the N3DS. I could be wrong, as I never bothered with the N3DS.