Why are these codes called "secret"? Simply, they are not needed by most ordinary users, they are not published in instructions to smartphones. First of all, "secret codes" are intended for engineers and developers for conducting various tests.
For Samsung, all codes are similar to the general ones, except for:
All common codes plus:
** 05 *** # Unlocking the PUK
Devices manufactured by Motorola have a special built-in menu, which you can enter by entering * # * # 4636 # * # *.
For Motorola devices, the following codes are also available:
This device also has a special convenient menu with switches. In order to enter it you need to enter one of the following codes: