i,

The recalbox is working fine in almost TVs here. But there is one tv, actually my room's tv, that when I turn on the Pi3 the inicialization screen appears but when the recovery screen disappears there is no image from the recalbox. I know that this Tv doesnt work with high values of resolution ( in the xbox, I have to put on the low resolution to works on this tv ) but I dont know how to change the recalbox's resolution. I tried to change this:

CEA 5 HDMI : 1920x1080 @ 60Hz 16:9, clock:74MHz interlaced

CEA 4 HDMI : 1280x720 @ 60Hz 16:9, clock:74MHz progressive

on the system config, but it wasnt effective.

I read the recalbox's manual and found this:

"You must connect the recalbox on a DVI screen but you have a black screen ?

Just edit the config.txt file, and comment the line
hdmi_drive=2
with a # :
#hdmi_drive=2

On recalbox v4.0.0, /bootpartition is on read-only.
So before editing your config.txt, you must mount your /boot partition with read-write rights.
Go on root acces, then type this command : mount -o remount, rw /boot"

But I didnt find this adress (/boot)!

and the second question

In which roms folder should I put the roms of the Nintendo 3DS?