I'm pretty sure the problems you were facing are precisely the ones I'm now trying to workaround.
Even after I import the seed using the latest version of FBI (I get a message stating "Seed Imported", so no apparent error is displayed) I keep getting stuck in a black screen, which comes right after the n3ds logo disappears.
Also, I don't understand why it is that the game I downloaded using the freeshop (or the official eshop) won't work either -- any other game I downloaded using the freeshop runs perfectly, even the most recent ones.
My 3ds uses the menuhax+rednand+autoboot (no A9LH here -- I used
Temptress Cerise's
tutorial). O3DS XL, CFW 11.1.0-34U, Luma3ds 6.3.1 and FBI 2.4.2 here, btw.
That said, could you please explain what it was that you did, exactly?
Following Amapola62's tips, I created a 'homebrew' folder. Inside of it I included a '3ds' folder. Finally, inside the 3ds folder I put a "Arm9loaderhax.bin" file, which was then renamed to "boot.bin". I didn't delete the "Arm9loaderhax.bin" on the root of the SD card, btw.
After that, I created a path.txt. I opened the file and there I wrote the following: "/homebrew/3ds/boot.bin" (without the quotation marks, obviously). Such file went to the "luma" folder that there exist on the root of the SD card.
Finally, (1) I inserted the SD card inside my 3ds, (2) accessed the homebrew menu, (3) launched the Luma3DS 6.3.1 and (4) marked the option "use custom path". I was then redirected to the CFW, where I launched the pokemon demo and... it worked!
HOWEVER, whenever I leave the demo and try to execute it once again, the black screen returns. What I have to do then is: reset the console, execute the homebrew launcher and, finally, launch the game.
So: isn't there an easier way to play games that demand more ram (for now, I really don't want to install A9LH...)? For example, isn't there a way the custom path can automatically be accessed (without me having to launch the homebrew menu every time I need to access the game)? How can I disable the boot loader and what is the downside of doing so?
I do want to migrate to A9HL eventually. However, I've already managed to put about every game to work, and I'm not so sure about going through an entirely new process once again.
Edit. I've just installed de A9HL. It was way easier than I thought it would be, and now the game runs smoothly. I'm glad I did it...