1. What We Need To Do.
i) We have 500+ units of a single model smartphone (NTT DOCOMO, SHARP SH-01L) with Android OS 10
ii) We need to downgrade all the units to OS 9
2. Issues We Are Facing.
i) SHARP, the manufacturer of the phone does not distribute the official ROM.
ii) OEM Unlocking feature is factory disabled (when you try to tap the toggle on the Developer Option, it's gray-out)
iii) There seems to be no download mode, fastboot option or anything equivalent (I tried with several combinations of physical buttons but nothing worked)
3. Your Requirements.
i) Experience in Android development
ii) Analysis of the architecture of the firmware
iii) You will have to let us know if you need all units delivered to your location and only you can operate the whole processes, or you can teach us how to downgrade the software with some required equipment
We have no idea how much this will cost so feel free to let me know your pricing.