Cannot open APK after software update

[user6OtMalm9cf]

Hi

I just installed the new Samsung software update in China. 

I re started my phone and it deleted my expressvpn app. 

It also won't let me open apk files of that nature either. 

How can I undo the software update or go back to the old software?

Thank you. 

[IsaacJunior]

You we will have to reset it to factory version. But make sure you back up every important files before doing that with your Samsung and Google account.

[user6OtMalm9cf]

How do I restore factory settings?

I am in China so cannot back up using Google. Is there any other way I can back up?

[IsaacJunior]

On your Samsung phone or tablet, open Settings and go to the Backup & reset or Backup and Restore screen. Under the Samsung account section, tap on the option for Backup settings or Back up my data. Go to cloud in settings and back up as well.
Caution: you need to backup all important stuff like WhatsApp.
Finally go to Factory data reset, and read how it works before resetting your device.

[user6OtMalm9cf]

But will resetting make it go back to the old software (before the update)? If not then there's no point