How to fix "Unfortunately (app) has stopped (read description please)

[Android Central Question]

It's not just one app but several apps. Whatsapp, line, gmail, playstore, google service, file manager, weather, gallery, any downloaded apps, and even settings. I've tried everything but none of it works. This is the list of attempts I've tried
1. Simply restarting the phone
2. Restart phone and tried to clear cache before I get "unfortunately setting has stopped"
3. Restart again and tried to clear data
4. Restart again just to see the app data come back so I try to uninstall the apps
5. Restart again just to see the apps and data come back again
6. Turn off the phone, go to recovery mode, and choose clear cache, then turn it on again. The caches are still there.
7. Turn off the phone again, go to recovery again, and this time I choose factory reset. But when I turn it on the apps and all of the data come back again and the problem persists.

I can't try to do factory reset from another device by email because I forget the password and the old sim card is dead so I can't recover the account.

So what should I do now?

(TL;DR Several apps stopped working, tried everything including factory reset but still have the same problem)

 

[B. Diddy]

Welcome to Android Central! Which phone, and what version of Android is it running?