How to Install App as System App My S3 has a damaged motherboard (says Samsung Tech Center), only boots into safe mode.

If I am to keep using the device I have to make the apps into system apps, so they run in safe mode.

One way is to use titanium backup (or other root file app) to make the app system, but the phone came back from Samsung wiped clean. It is still rooted, have SuperSu app installed.

Does anyone know how I can make a Play_Store or Downloaded_APK app system?
Carl Parker writes about it on Android Authority:
(partly reproduced here in case the original post goes down)


  For Apps Installed on the Device  
  
  
  Assuming you have installed the app on your device, go to the app’s
  Google Play Store link and take note of the words after “?id=” and
  ignore the rest.  
  Connect your device to the computer via USB
  cable. 
  Open the command prompt on your computer and type the following
  commands: 
  


adb remount 
adb shell 
su 
cd /data/app/ 



  
  Type the command ls appfilename* (where “appfilename” is the app’s ID on Google Play
  Store; make sure you include the asterisk at the end).  This command
  will display the app’s complete APK filename.   
  Enter the following command: 
  


mv apk_full_filename_here /system/app/apk_full_filename_here 
exit 
exit 
adb reboot 



  
  The device will now reboot. Your app is now saved as a system
  app. 
  
  
  For Apps Whose APKs Are on the PC Hard Drive
  
  
  Open a command prompt on your computer and navigate to where the APK
  file is located. 
  Enable USB debugging on your device and connect your
  device to the computer via USB cable. 
  Enter the following commands:
  


adb remount
adb push apk-filename-here /system/app/
adb shell chmod 644 /system/app/apk-filename-here
adb reboot



  Your phone will automatically reboot. Your app will now be saved as a system app.