STOP AND DO NOT INSTALL THIS APP UNTIL YOU READ THIS!!!
By default, there is no multi-user option in Oppo A1k. I tried to use a third party Google Play App “Hidden Settings For Android”. When I clicked on the Guest Mode, the phone went in the unusable state. Thankfully, there were “Settings” option available from the top-down swipe where I selected;
Settings –> Additional Settings –> Automatic on/off – Auto Power-off
And then I selected two minutes later time to turn my phone off automatically so that I can restart and uninstall this buggy phone app called “Hidden Settings For Android”.
Totally not recommended for anyone.
This app’s developer name is “Common Tools” firstname.lastname@example.org from Massachusetts Institute of Technology.