Removing an app protected from uninstall by password and with System Owner permissions? I want to ask, if there is a way to remove an app that is protected from uninstall by password and has Device-administrator permissions granted? 
I am using an LG L90 phone with android 5.0.1 L (NOT ROOTED) Apparently it has a safe mode, as 1 year ago I accidently booted into it.

So here is the story what happpened:
I am developing an application that is supposed to limit access to for example work phones. It is password protected from uninstall, and I am regularly testing it on my phone. But in the most recent version, a bug slipped in which broke SHA256 hashes and caused passwords to be not recognized by the app, which means that I have locked myself out of games and youtube. Is there a way to remove this application? (Keep in mind that it has device administrator permissions and pops up with lock-out screens when on the "App uninstall" screen).

If the safe-mode thing could help, how would I boot into it?
Of course you can uninstall from the safe mode. Disable the authorization in the Device Administrator first.

Step for booting in safe mode:


From any screen, press and hold the Power key.
Touch and hold Power off. Review the 'Reboot to safe mode' screen,' then tap OK. 
The device should restart in safe mode and 'Safe mode' will appear in the lower-left.
Uninstall the app that is causing a problem.