Why my setting app logo has changed to android logo?

[Android Central Question]

A few days ago my setting app logo has changed to android logo and it is also not woking now and whenever i open it it shows .com android.setting has stopped and i also cannot delete it because it is my tab's permanent app and it cannot be deleted from my tab please help me and also one thing recently i updated my tab software and it didnt work so i changed the software of my tab my tab is huawei media pad 7