Let’s start by explaining what is USSD (Unstructured Supplementary Service Data). It is a protocol that allows information to be sent across the network. It is for example possible to recharge your phone in call credit in certain countries. Thanks to this protocol, we buy a card, we scratch and we enter the code.
In the same way, there are some codes that we can use to access information, do tests or access hidden menus in our Android phones. Some codes will refuse to work on certain models or brands of smartphones, but you can try them carefully. You could lose data or damage your device. Do the manipulations only if you are absolutely sure of yourself.

See the full codes here »» https://www.dominzyloaded.com/2020/03/android-secret-codes-you-dont-know.html?m=1