Fake 3DS games have not been documented. It's unlikely that fake 3DS games exist due to the nature of how the games are produced as both the cartridges and consoles are encrypted unlike the DS-line. As such, compared to other entries in r/gameverifying's wiki, this will be a relatively smaller section. We will add any information we can find on the 3DS games here.
Nintendo 3DS carts are similar to the Nintendo DS carts, however they are mainly white and have a rectangular tag on the right side of the cart. 3DS carts use the model code: CTR-005.
Teddy Together for 3DS, PAL. Front face.
Teddy Together for 3DS, PAL. Rear face.
White for both PAL and NTSC/J. PAL cases are slightly thicker - this may vary for different games.
Duck Dynasty for 3DS, NTSC. 12.4mm case width.
Ghost Recon: Shadow Wars for 3DS, PAL. 15.4mm case width.
New Nintendo 3DS
Black for both PAL and NTSC/J.
Opening a 3DS Cart
Like the entry for the DS carts, this goes without saying, that we highly recommend that you do NOT do this!!! The reason why we don't recommend this is because the rear and front casings are "hot-welded" together, meaning that if you break the seals apart in order to get into the cart (which is 99% likely), you won't be able to re-close the cart. Got that? Ok, let's continue...
At the top left of the cart, you'll see a slight indent. What you'll need to do is, with a plastic spudger (you can use a metal spudger, but this will further damage the plastic of the cart), gently pry apart the front and back casings apart. You'll very likely snap the fused parts apart. Once these parts have come away, you'll need to pry open the left side of the cart. The next part is to pry and slide your plastic spudger underside the botom of the cart apart until you're near the right side. Then the right side of the front of the cart should be able to be unclipped off of the back along with the side tag. Once unclipped, you should be able to see the board.
However, if you do wish to replace the 3DS cart casing, you could use a third-party casing. The linked casing is the same one we "recommend" for the DS carts, and does not show any Nintendo markings along with you having to create your own reproduction sticker. This will show that your game is custom, but if you're looking at custom 3DS cart cases you already know that. We don't really recommend it, but we're just showing you that the option is there.
Front-side of the PCB for Teddy Together. Note the 4x gold rectangles found on GameBoy games, legit.
Back-side of the PCB for Teddy Together. Almost indistinguishable from a DS PCB.
3DS games are sealed using Y-folds. Sealed NTSC games do not carry the Nintendo tearaway strip.
Awaiting images for the sealed NTSC games
3DS games are sealed using Y-folds. Sealed PAL games do carry the Nintendo tearaway strip in grey, along the bottom third of the casing.
Teddy Together for 3DS, sealed PAL.