https://ja.wikipedia.org/wiki/DM-01H
Hardware similar to SHARP Aquos Compact SH-02H
Latest 01.00.06
https://k-tai.sharp.co.jp/support/developers/oss/dm01h/index.html
By buttons: Phone in off state. Hold Power and Volume Down until two vibration. Reboot and hold Power + Volume Down don't work
Under shell: adb reboot recovery does not work
"OEM unlock" option can be found in the Developer menu
By buttons: Not found
Under shell: adb reboot bootloader does not work
By buttons: Not found. Phone in off state, plug in USB and hold power for 1 second not work.
Under shell: adb reboot edl works for 01.00.04 but not work for 01.00.06. For 01.00.04, Qualcomm HS-USB QDLoader 9008 detected but no leaked rom so far
*#*#13491#*#* or *#*#717717#*#* does not work
/sys/class/android_usb/android0/* requires root privilege
setprop sys.usb.config diag,adb requires root privilege
Tried: Kingoroot, Kingroot and Root Genius. All failed
Temporarily save at /sdcard/PRIVATE/update_package but the phone will reboot and start update soon after download complete. The connection is encrypted. Man-in-the-middle proxy will cause download stopped. Not sure it uses HTTPS or other protocol so unable to backup the OTA package.
Seems this guy has some useful codes to decrypt the OTA update, it needs old version of LZMA to compile SHARP FOTA parser DEMO