Android 12 update

Thanks, ihateandroid12update, for bringing up your software installation issues, as we value your feedback and comments here.

And it's unfortunate you are having inconvenience dealing with non-working power button and apps crashes, that you initially expect it to be normal after each update.

There are so many ways, we can figure out what's behind the problems you've encountered and one of those is that Samsung neither recommend nor provides downgrading procedure of OS in device after an update. 

I strongly advise to bring your Samsung Galaxy A03 device immediately to Samsung Authorized Service Center near you. Our Samsung Engineers are competent to restore your device back to its intended operations with the excellent service available.

https://www.samsung.com/ph/support/service-center/ 

And/or call any of our support channels by clicking any of the links below.

https://www.samsung.com/ph/support/contact/#onlinesupport

https://samsung-livechat.sprinklr.com/seao/ph/index.html 

Hope we satisfy your inquiry and your problem gets solved soon.