Can I create a general configuration file and use it for all my devices?

No, each Grandstream device should have its own unique configuration file. It contains the device’s identity, ensuring that the configuration file is truly intended for the receiving device. This is a security measure.

How can I prevent end users from modifying specific settings like SIP Account Credentials?

Enable “Keypad Firmware Update Lock” (P88) to prevent users from performing factory resets through the IVR.
Change the Administrator password (P2) to restrict access to the Advanced settings web user interface.
Add a P1 value to configuration files to ensure that devices only accept configuration files with a matching password.