You could dd the partition hosting the rootfs & the kernel. (Cf.
https://wiki.mobileread.com/wiki/Kind...Hacking#Backup).
I don't actually remember if there's a separate diags partition on the K2, will dig up my k2i tomorrow. But since this appears to be a proto/dev board, check the partition layout before.
As knc1 said, this is a non-public build, so I don't expect any of the official OTA updates to provide a starting step corresponding to it, which probably explains why the update failed. (Check the logs to make sure [showlog over SSH]).
EDIT: Yup:
Code:
02/update-02-399380047-431100003.bin
02/update-02-431100003-472900057.bin
02/update-02-472900057-490480060.bin
02/update-02-490480060-501100064.bin
02/update-02-501100064-501108064.bin
02/update-02-501108064-550650009.bin
02/update-02-550650009-555370010.bin
No 446420037 anywhere

.
The tags were a mess at that time, so I'm not quite sure what we'll be able to tell from it, but could you post the output of /proc/boardid?