Fire HD 6 - UnDemo ?

Hi have been searching but haven't found much on these.
Have two of these so far from a Uk Retailer for processing. Model PW98VM

Is it possible to transfer the stock update file on to these si when rebooted the update is detected and installed.

a little research shows that the JDebug connections have TX on Pin 5 and RX on Pin 4. I used GND off one of the shields. Then using the standard adaptor managed to solder fine wires onto the solder pads. Then using Putty with the settings for the ereaders had data on booting.

Interestingly with the factory cable connected it booted into Linux

TargetStart=80208000
FreeStart=810FB640
FreeEnd=8110B640
DataStart=80C3E9AC
Uncompressing Linux... done, booting the kernel.
ootprof.lk_t=1719 bootprof.fp_t=10282[1460] lk boot time = 1719 ms <
/system/bin/sh: [1460]: not found
127|shell@android:/ $ [1460] lk boot mode = 8
/system/bin/sh: [1460]: not found
127|shell@android:/ $ [1460] lk finished --> jump to linux kernel
/system/bin/sh: can't create jump: Read-only file system
1|shell@android:/ $
1|shell@android:/ $ TargetStart=80208000
shell@android:/ $ FreeStart=810FB640
shell@android:/ $ FreeEnd=8110B640
shell@android:/ $ DataStart=80C3E9AC
shell@android:/ $ Uncompressing Linux... done, booting the kernel.
/system/bin/sh: Uncompressing: not found
127|shell@android:/ $ shell@android:/ $
/system/bin/sh: shell@android:/: not found
127|shell@android:/ $

or is this ADB mode ?

What I'm looking to do is put stock firmware on these without if possible changing / unlocking bootloaders.

Can anybody offer and help.
Loading the TWRP app is not possible due to the Demo software.

Thanks for any help ,and if I've missed something on here (went back in this section back to launch date) then please point me to the relevant section.

Cheers