Passcode
My phone suddenly changed the passcode on its own. I am so confused. I didn’t know that apple does that. How can it be fixed without erasing the content of my phone. And how to avoid it from happening again
iPhone 12 Pro, 14
Apple doesn't do that and it didn't change on its own.
You will need to reset your phone. Hopefully you made ba kups so you can restore your data.
If you forgot the passcode on your iPhone, or your iPhone is disabled or unavailable -
How to reset your passcode without a computer if you have iOS 15.2 or higher.
How to remove your iPhone, iPad, or iPod touch passcode without a computer - Apple Support
How to reset your passcode using a computer.
If you forgot your iPhone passcode - Apple Support