I report my result ; the cable which is next to the uppeer display backlight cable is not necessary .
Speakers may be removed by mistake but the speaker ribbon cable are necessary.
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The mic is not necssary.
I am using NEW3DSLL but the camera is not necessary in my case although I do not know why.
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The NFC cable is not necessary.
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I post many times because I report as soon as I find something.
As
Ryccardo teached me, the backlight cable is necessary but the 2 others of the bottom display are not necessary.
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The upper display also requires only the backlight cable as the bottom display does.