Questions about sony linux

[Firmware]

Hi I have a few questions regarding Sony Linux for those in the know

I have a nwz-a20, with rockbox installed

in the service menu there is a setting called SMPCHGCH Smart_Stent, I don't think the service menu retains these settings

in the service manual it's described as this:

4-1-5. Smart phone charge/discharge function check
(SMPCHGCH)
Note: Not used in this unit.

n.b. - there is quite a few service features that are "Not used in this unit"

is there a command with the SonyNWDestTool to set this setting permanently?

Is there a list of all known SonyNWDestTool commands?

as my a20 is dual booting, should the SMPCHGCH setting only be invoked by loading into the sony gui? or is it the case that by the time the time I get to the boot menu SMPCHGCH has already run it's course?

I'm not a coder or a linux pro, though I'm learning all the time, so this a question for the devs, have you guys managed to get to the point over usb, or some other method, where you can get a terminal root connection to the sony linux os?

I know sony posts the source code (sort of) as I understand it here https://oss.sony.net/Products/Linux/Audio/NW-A25.html

from that, could you guys rebuild the entire original sony firmware? or is there more to it than that?

Thanks

[Firmware]

I forgot to mention, has sony ever posted the source for the service menus anywhere?

Thanks