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

No, each Grandstream device must have its own configuration file. It has the device identification burned in. This is a security measure to make sure the configuration file is really intended for the receiving device.

How can I lock the end users from changing certain setup, such as SIP Account Information?

. Turn on "Lock Keypad Update" (P88) to prevent users from doing a factory reset via IVR.
2. Change Admin password (P2) to prevent access to ADVANCED settings web UI.
3. Add a P1 value in configuration files so that devices only take configuration files with a matching password.